Easter Weather in Southern California: Rain, Heat and Everything in Between

_{Beautiful spring colors visible on Good Friday 2024. Photo from Daniel Coats}

Whether in late March or April, Easter falls within spring weather patterns, and in Southern California, that typically translates to either mild sunny days, cloudy and chilly but dry days, or some mixture of the two.

But over the generations, there have been some unique weather conditions that have greeted Southern Californians celebrating the resurrection of Jesus Christ on Christianity’s foremost annual holiday.

Looking specifically at my hometown of Riverside, where weather records have been kept since 1893, here are some of the most notable Easter conditions.

Rain

March 31, 2024, was the first Easter since April 16, 1995, when significant rain fell in Southern California.

Many lowland areas received between one and three inches of rain in a two-day storm, while up to two feet of snow fell in the mountains, creating a weatherscape that might seem more emblematic of Christmas than Easter.

It was also the second-coldest Easter daytime temperature on record, with a high of only 54°F.

For those old enough to remember, the sunrise services moved indoors were reminisicent of the situation in 1995, when snow snarled the mountain passes, high winds knocked out power in some areas and frozen precipitation was observed as low as 1,500 feet.

That Easter would mark the beginning of a very pivotal week in American history. On April 19, the Oklahoma City bombing would forever change America, marking an end to innocence and the arrival of terrorism on U.S. soil.

Other rainy Easters since World War II occurred in 1982, 1981, 1969, 1963, 1958, 1957, 1956 and 1950. But in many cases, those rainy days only had a few hundredths of an inch, often in the mornings amidst fog and low clouds that gave way to sunny (or partly sunny) afternoons.

At least in Riverside, the wettest (and coldest) Easter was March 27, 1910, when the high temperature was only 52°F and 0.94″ of rain fell.

_{Snow is visible on the San Bernardino Mountains on the Saturday before Easter in 2024. Photo by Daniel Coats}

Cold

Cold and rain often go together in Southern California in spring – but not always.

On March 27, 1921, Easter morning was a chilly 33°F, with below freezing temperatures in many spots. But the afternoon was a sunny and warm day.

Of course, prior to the 1950s, cold nights were more the rule than not in Riverside, as the urban heat island had not yet developed since the land was mostly citrus groves, rather than cityscapes that trap in the heat of the day.

Heat

Since early/mid spring can also be a time for (usually gentle) Santa Ana winds that can quickly raise temperatures to summer-like highs, there have been some very hot Easters in the Southland as well.

The record for Riverside goes to Easter 1936, when the temperature was 98°F on April 12, 1936. It was also 95°F on Easter 1930 (April 20, 1930) and Easter 1962 (April 22, 1962). And on Easter 1961, it was 93°F, but the following day, it reached a downright hot 100°F.

A map showing where the 2010 Easter earthquake was felt.

The Easter Earthquake of 2010

On Easter 2010 (April 4, 2010), Southern Californians were rattled by a strong earthquake, which for many was the first quake they felt that originated outside of the Golden State.

The Magnitude 7.2 quake during the afternoon was centered in Baja California, and caused moderately extensive damage in Mexicali, and lighter damage in the Imperial Valley towns of Calexico and El Centro. It was felt widely in Southern California, Arizona, Nevada and other parts of the Southwest U.S.

Old timers might also remember the Good Friday earthquake of 1964 in Alaska. Though thousands of miles from Southern California, the quake (Magnitude 9.2) was one of the largest in recorded history, and was instrumentally detected around the world. Tsunamis were reported throughout the Pacific Rim, including in the Los Angeles, Orange County and San Diego areas.

Southern California’s Second Coldest Winter Ever?

A once-in-a-lifetime snowfall at the University of Redlands in February 2023.

If you were in Southern California over the past nine months, you’ve noticed the persistently chilly, cloudy and often rainy or snowy weather.

Even longtime residents often felt it was the coldest winter they had experienced.

And according to data from Riverside’s March Field, they weren’t wrong.

Official data from major cities such as Los Angeles, San Diego and the South Coast Metro reveal that 2022-2023 was in the top 10% of coldest winters, with data typically going back to the 19th century.

But that understates the coldness (by California standards) that occurred this past winter, because most weather reporting sites in the Southland metro are as much as 10°F warmer on an average winter night than a century ago due to the urban heat island effect.

Mile after mile of blacktop and concrete, with relatively few trees due to the typically dry climate of Southern California, made nights dramatically warmer between the 1950s and 1980s and continuing to present.

To get a true feel for how cold this past winter was in the natural environment, we need to look at weather records in places relatively unaffected by the urban heat island.

One such spot west of the mountains is Riverside’s March Field.

While warehouses are being built in that area in recent years, there remains significant agriculture and open lands, much more typical of the region in yesteryear.

There, 2,508 heating degree days have been recorded from July 1, 2022 to late June 2023.

A heating degree day is a measure of how cold it was on a given day or over a longer period by averaging the high and low temperature of each day and comparing it to 65°F.

So a typical Southern California winter day might be 68°F in the afternoon and 45°F at night. That would translate to eight heating degree days.

The most heating degree days reported in nearby Riverside (back before urbanization) was in 1949, when 2,521.50 was recorded. That was the year with the most widespread snowfall recorded west of the mountains. And that year had only 13.5 more heating degree days than this past winter (in other words, just one or two more cold days).

So if you felt this past winter was extraordinary, you were right!

Probably a lot more like the climate in the 1500s to early 1800s, when the Little Ice Age resulted in colder temperatures than usual in the past 2,000 years. Of course, we don’t have daily weather records from back then.

And It’s Been Cloudy Too

Cloud cover isn’t as quantifiable as temperature or rainfall.

But it makes a big difference in what the day-to-day weather feels like.

And over the past nine months, typically sunny Southern California has had a very different feel.

This data from San Diego is probably a bit cloudier than inland spots. But it gives a good look at what the situation has been like.

And San Diego really hasn’t been sunnier than major cities in the Great Lakes or Northeast this past year.

Where We Stand with Rainfall

2022-2023 wasn’t the wettest year on record in most places in Southern California. But it was among the top 10 in a lot of spots.

Recently, the water year has been redefined as October 1 to September 30.

But for those of us used to July 1 to June 30 as the water year, here’s where we stand at Downtown Los Angeles.

Wettest Seasons (Period: July 1 to June 30 of following year)

Since first recorded rain season, 1877-1878

Total Inches of Rainfall	Season
38.18	1883-1884
37.25	2004-2005
34.84	1889-1890
33.44	1977-1978
32.76	1940-1941
31.25	1982-1983
31.01	1997-1998
28.40	2022-2023
27.47	1968-1969
27.36	1992-1993

Source: L.A. Almanac

The Historic Southern California Blizzard of 2023

This photo of snowfall near Leroy and 34th in the city of San Bernardino is truly amazing, considering this is an altitude of about 1,500 feet! Photo from February 2023

The words “blizzard” and “Southern California” don’t seem to go together. Even more so when we consider the lower elevation valleys and foothills. But late February 2023 will go down in Southland history as the time when an almost unbelievable weather phenomenon brought heavy snowfall to low altitude communities across the Inland Empire and Los Angeles County with a depth and widespread coverage not seen since January 1949.

As the region’s climate has warmed due to the urban heat island effect (cities are always warmer than surrounding countryside due to blacktop, the built environment, etc.), and the suspected effects of global climate change, many weather experts have expressed skepticism that the region would ever see significant or widespread valley snowfall again. Indeed, the conditions for such an event are very particular and might not occur for decades even before urbanization and industrialization.

But on Feb. 22, the rare conditions became a reality as a very cold storm, yet wet enough to generate substantial precipitation, arrived in the region. Many foothill towns, down to an altitude of 1,000 feet in some spots, picked up light to moderate snow, with of course much heavier accumulations in the mountains.

This map from NBC Los Angeles’ radar shows the snowfall that occurred on the night of Feb. 22-23.

Snowfall map for Feb. 22-23, 2023. In addition to usual mountain spots, many lowland areas of the Inland Empire and the Santa Ana Mountains between Orange County and Riverside received significant snowfall.

The following day dawned crisp and partly cloudy in most spots, along with the realization that snow had fallen in some surprising spots, including the foothill towns of the San Gabriel Mountains, the Santa Clarita foothills, Moreno Valley, Perris, the agricultural parts of Riverside, and the Hemet area.

Following a period of warmer but rainier weather on Feb. 24, a cold front sweeping through on the morning of Feb. 25 brought an even deeper and more dramatic snowfall to virtually the entire Inland Empire east of the I-15 corridor, as well as many higher elevation valleys in Los Angeles County.

Snowfall map for Feb. 25.

Just a few days before this almost alpine scene was photographed, temperatures were sunny and in the 70s, classic Southern California early spring weather! Photo from February 2023

Campuses such as Cal State San Bernardino and the University of Redlands turned into winter wonderlands. A coat of snowfall on the Victorian and Spanish revival homes of the Inland Empire’s downtowns were a particularly memorable image.

For only the second time, a blizzard warning – for a combination of high winds and snow – was issued for the San Gabriel Mountains, the range behind Los Angeles. The first blizzard warning on record was instituted for the San Bernardino Mountains. Less severe winter weather advisories were put in place for valley and Inland Empire communities.

Areas in the Inland Empire near Fontana, Rialto, and Devore have now picked up more snow this winter than New York City and Philadelphia.

Y'all can have it back now @NWSNewYorkNY and @NWS_MountHolly

Latest rain and snow totals here: https://t.co/UAtQmHTkpx#CAwx pic.twitter.com/czekgGcilU

— NWS San Diego (@NWSSanDiego) February 25, 2023

Seriously, this is unbelievable! Low elevation areas under 2,000 feet received more snow during the February 2023 storms than New York City and Philadelphia received over the winter!

But even that wasn’t the complete saga of the Southland’s exceedingly rare snowfall. On March 1, as the last storm of the season exited the area, rain surprisingly turned to snow during the afternoon in some surprising areas, including Disneyland, which saw some graupel for the first time ever! (It snowed in Anaheim in 1949, but back then, Disneyland did not yet exist, because the park opened in 1949)! Ice on windshields at midday in North Orange County was an exceedingly rare sight!

The freak snowfall of February 2023 has been part of an overall wetter winter that is making headway against the chronic drought that has bedeviled Southern California for the past 25 years. From a water supply standpoint, the Sierra Nevada snowpack, not unusual accumulations in the valleys, are what matters. Still, the snowfall of February 2023 will add a new layer to the complexity of Southern California weather and climate, already among the toughest to predict due to the sharp differences from season to season. Despite a changing climate, the recent snowfall has added humility to predictions, demonstrating that once in a generation cold waves can still happen in the 21st century.

Perhaps this event is similar to the cold wave that struck Texas in February 2021, which brought the coldest temperatures recorded in the Dallas area in 72 years. That event, like the February 2023 California snow, was not truly unprecedented in the historical record. But it was the first in living memory, and it was a type of weather condition widely unexpected to recur.

Together, these events are a reminder of the complexity and uncertainty involved in climate prediction.

Results of a LinkedIn poll in the aftermath of the rare snowfall that showcases public perceptions of the event in relation to climate change.

A light dusting of snow at Kimberly Crest mansion in Redlands on Feb. 25, 2023.

One lesson from the Blizzard of 2023: Even a few hundred feet of elevation makes a difference in Southern California. Homes such as this one in the affluent South Redlands neighborhood retained a coat of snow for hours, while snow melted quickly in the nearby downtown. Photo from February 2023

SNOWFALL TOTALS FOR THE BLIZZARD OF 2023

MOUNTAIN AREAS
Mountain High Resort	93 inches
End of Mt. Baldy Road	77 inches
Running Springs	71 inches
Lake Arrowhead	68 inches
Crestline	63 inches
Big Bear	40 inches
Mount Wilson	40 inches
Forest Falls	36 inches
Mt. Baldy Village	27 inches
Oak Glen	26 inches
LOWLAND AREAS
Devore Heights	12 inches
Fontana	2 inches
La Crescenta	2 inches
Rialto	1 inch
Bloomington	0.5 inches

SOURCE: National Weather Service San Diego; National Weather Service Los Angeles; media reports

Want to See Snow Without Braving Mountain Roads? Here Are Seven Options During Low Altitude Snowfalls in Southern California.

A snow-covered Mt. Baldy visible from Mt. Rubidoux in Riverside. Photo from December 2019

This week, snowfall is expected at very low altitudes (as low as 1,000 feet in some spots). That means that while the Los Angeles, Orange County and San Diego metro areas won’t likely see snowfall, many outlying communities will. With predicted low snow levels, here are some spots to check out if you want to see the white stuff and don’t want to brave treacherous mountain roads.

(But please…don’t block roads and respect private property).

LOS ANGELES COUNTY

Higher elevation portions of the Santa Clarita Valley are as much as 2,000 feet high, and so can get a dusting of snow.

Mt. Baldy Village (elevation 4,193 feet) is technically in the mountains, but the drive up Mt. Baldy Road is quite easy. Hiking trails, Native American cultural displays, and a mountain-themed restaurant with live music enhances the experience.

ORANGE COUNTY

Silverado Canyon lies between 1,000 and 2,000 feet in altitude in a steep and shady valley. Snow has been known to occur here from time to time. It’s a very interesting country-style town in the midst of Orange County.

The Ortega Highway in the Santa Ana Mountains often receives winter snow and isn’t too challenging if approached from San Juan Capistrano.

It’s rare but not unheard of for heavy snow to fall in the hills between the Inland Empire and Orange County, as this photo shows. Photo from December 2019

INLAND EMPIRE

At more than 2,000 feet in altitude, Devore (near the intersection of the I-15 and I-215 freeways) has a number of parks where snow can be experienced during low altitude falls. Even the campus of California State University-San Bernardino can occasionally see snow! Especially at the observatory, accessible by a short uphill walk from campus.

The communities of Yucaipa, Banning, Beaumont and Calimesa receive snowfall one or two times in most winters. Each of these communities has great downtowns to check out on any visit, in addition to experiencing some snow.

SAN DIEGO COUNTY

Julian (elevation 4,226 feet) is a mountain town without the mountain drive. Great to visit at any time of year, it receives HEAVY snowfall on several occasions in most winters. This is the best snowy day trip from San Diego during cold winter storms.

A light dusting of spring snow near Cal State San Bernardino. Photo from Feb. 2022

P.S. – Snow may be rare at low altitudes in Southern California, but frost isn’t. Where I live, there has been a blanket of ice on at least a few dozen mornings this past winter. Maybe a bit more than usual, but certainly icy mornings aren’t unheard of. The best place to see frost on a cold winter morning is in the Arlington Heights area, which is still farmland, so it gets colder than the nearby cities.

The World’s Largest and Most Famous Thermometer in a Small California Desert Town Recalls the World’s Hottest Temperature

_{The Baker Thermometer breaks the monotony of a desert drive with a reminder of the extreme temperatures recorded in this region of California. Photo from October 2022}

There isn’t much of note in Baker, California, to put the town of 735 people in the Mojave Desert on the map. If it weren’t a rest stop on the way from Southern California to Las Vegas, it is doubtful that many people would find reason to visit here. But Baker’s claim to fame is an impressive one: It claims to be the site of the world’s largest (and most famous) thermometer, which records the world-record 134°F temperature observed in nearby Death Valley in 1913. Weekenders, truckers and business travelers are reminded of the extreme temperatures in this part of California when they see the current temperature (which quite often is well into the 100s) compared with the all-time record.

Baker was founded in 1908 as a station on the Tonopah and Tidewater Railroad. It has been the site of the iconic thermometer since 1991. The 134-foot-tall steel electric sign was snapped by hurricane-force winds in 1993, but was rebuilt. More recently, it was renovated for a digital display.

Situated at the intersection of State Route 127 and Interstate 15, the town is the gateway to the expansive Death Valley region to the north. Baker itself sits at an altitude of 930 feet, much lower than Barstow or Las Vegas but higher than the 282 feet below sea level at Death Valley’s lowest point.

Therefore, Baker might be considered one of the “cooler” sections of the Death Valley region. Still, temperatures here have hit 125°F and average above 110°F in July.

A visitor to this community will find a town that has seen better days. Once the site of a major prison, Baker today is in decline, with many motels and shops of yesteryear permanently shuttered.

_{Though Baker may be in decline, it is forward-thinking enough to have an electric vehicle charging station. So Baker is a great place for Tesla owners to explore! Photo from October 2022}

_{The brutal 134°F recorded in Death Valley in 1913 is so ingrained in the identity of the small nearby town of Baker, California. Photo from October 2022}

But the thermometer, visible for miles away in either direction on the I-15, still makes this spot a great place to get out, take a stretch, and get a selfie or group pic. And perhaps buy a souvenir at the nearby gift shop. And maybe even plan your own excursion to the heart of Death Valley some 115 miles to the north.

I’d advise against visiting in midsummer. Despite a rush of interested tourists, the temperatures are just too extreme to enjoy safely. Come in the cooler months instead. Grab a bite to eat at one of the fast food establishments or the Mad Greek Mediterranean restaurant. And perhaps stay for the sunset, which is particularly beautiful here.

Baker is a reminder that every place – no matter how seemingly inhospitable – is unique and interesting. And that any superlative can be a locality’s claim to fame – and make it worthy of exploration.

_{A look at Downtown Baker. Photo from October 2022}

Tornadoes in the Southland: A Look at Southern California’s Twister History and Risk

A funnel cloud in Roseville, California, in 2014. Photo from Wikimedia Commons

Residents of South Central Los Angeles are used to unrest and damage. But on March 1, 1983, the neighborhoods south of downtown experienced a surprising disaster. Instead of riots, earthquakes or fires, residents were startled by the devastation of a significant tornado.

Homes and businesses were destroyed, cars flipped, and the roof ripped off the Los Angeles Convention Center.

The storm was estimated as an EF2 on the Enhanced Fujita Scale – the five-point scale used to measure twisters. That’s nowhere near as bad as the worst of the worst in the Midwest or Southeast. But it was bad enough to leave nine people dead, 30 injured and tens of millions of dollars in damage. The path of destruction followed the 110 Freeway, coming just shy of the core of downtown.

While an astonishment to many residents and visitors alike of the city that was scheduled to host the Summer Olympics the following year, the whirlwind wasn’t the first to strike the City of Angels or the Golden State. In the nearly four decades since, many others have traversed the state, sometimes doing modest damage.

Here’s your guide to California tornadoes: When, where and why they happen, and how to prepare.

Understanding Tornadoes – Nature’s Most Violent – and Localized – Storms

Tornadoes are a different beast compared to large-scale weather features such as frontal systems or hurricanes. They’re hard to forecast with any precision. And they are hard to attribute – or not – to global trends such as climate change. That’s because they are so small. The average tornado is about 500 feet wide and travels for about 5 miles. That’s just a tiny fraction of the size of other weather features.

But despite their modest size, the impact of tornadoes is anything but small. The level of damage caused by a major tornado is only equaled by nuclear or meteor impacts. Winds of more than 200 mph can result in near total devastation.

The central and eastern U.S. are at particularly high risk for catastrophic tornadoes because North America is the only continent without a major mountain range separating cold polar air masses from warm tropical ones. The clash of these temperature extremes results in severe thunderstorms – and thus tornadoes.

But anywhere there are thunderstorms, there can be tornadoes. And that includes California.

California Tornadoes 101

During the 1991 to 2010 period, California averaged 11 tornado reports per year. The risk is mostly between January and April, during winter and spring Pacific storms, though twisters have been seen in the state at other times.

Stretching 450 miles across the state’s midsection, the Central Valley mimics the Great Plains in many respects: It is the state’s breadbasket and salad bowl – a lush agricultural heartland. And it’s the area of California virtually devoid of mountains or hills. It’s also where the bulk of tornadoes occur in the Golden State.

But for a single county, Los Angeles leads the way in tornado reports. Perhaps that shouldn’t surprise us – 10 million people and the capital of the entertainment world means even the smallest weather phenomenon won’t go unnoticed. But there is also an anomalous risk in some coastal areas, including Long Beach, South Los Angeles and Whittier. Since 1950, 43 recorded tornadoes have hit the county (others are more anecdotal and might include funnel clouds that never touched the ground). 1983 was the worst, and 1966 had the runner-up.

Where California’s tornadoes occurred over a 24-year period.

Another risk area is in the Inland Empire, with Lake Elsinore, Perris and Hemet – communities prone to violent summer thunderstorms – also sometimes experiencing tornadoes.

Coastal areas often see waterspouts – tornadoes that occur over the ocean. Many times, these are stunning to photograph – from a safe distance. Occasionally, however, they move over land, resulting in destruction.

If you’re seeking to stay safe from tornadoes, head to the mountains. Twisters are virtually unheard of in mountain communities. However, the same thunderstorms that bring lowland tornadoes can deliver mudslides to higher terrain.

Being Prepared

As throughout the country, Southern California National Weather Service forecast offices issue alerts for all types of severe weather, including tornadoes. A tornado watch means conditions are ripe for twisters, while a warning means one has actually been sighted.

Since tornadoes are so hard to predict, it’s common that warnings are issued without watches, but usually the weather forecast will mention a risk of thunderstorms that day.

Afternoon is the highest risk time, with sundown significantly lowering the risk, as the thunderstorms that spawn tornadoes thrive in the heat of the day. But as with location, same with time of day. There’s a chance at any time if the conditions are right.

Unfortunately, most homes and buildings in California don’t have basements. But there’s still ways to stay safe. Head to an interior room away from windows (such as a bathroom) and seek shelter until the danger has passed.

To the Future

While climate change connection to tornadoes anywhere is tricky business, one trend seems clear: The highest risk areas in the U.S. are shifting. That means stereotypical “Tornado Alley,” comprised of Texas, Oklahoma and Kansas, is being supplanted by the Southeast and Midwest as the new danger zones.

That’s bad news for the U.S. as a whole, since the new at-risk areas are more heavily populated and don’t have the advantage of miles of open prairie, where twisters can be spotted far in the distance, allowing plenty of time to prepare.

In California, the future of tornadoes is more uncertain, since they aren’t all that common to begin with. Generally, years with heavier-than-average rainfall can be expected to have more tornadoes in California, and the reverse is true of drought years.

It’s unlikely that tornadoes will ever rank among the most serious natural hazards in the Golden State. But as in every other state, twisters do pose a risk in California, too. And its residents and visitors should always be prepared.

Photographing the Fog: Five Places to Head When Southern California Looks Like London

Riverside’s Hunt Park on a foggy morning. Photo from Nov. 2021

Despite Southern California’s reputation for sunshine and warm temperatures, every year – even drought years – brings a number of mornings with dense fog, especially along the coasts, in the valleys and on the west slopes of the mountains. Locals associate these episodes with the marine layer and they are most common in spring, but can occur in any month.

For commuters, receiving a smartphone alert of a dense fog advisory usually means a worse than average morning commute, with the risk of accidents.

But for the professional or amateur photographer, Southern California fog is an opportunity to capture memorable images of the region in a very different setting than typical.

Here’s your guide to capturing a unique “slice of life” during those unique and quietly beautiful mornings.

A Look Back at Southern California’s Wettest Summer on Record

Flash flooding under a bridge near Riverside, California, during Hurricane Dolores. Public domain photo from Cal Fire

In my hometown of Riverside, California, precipitation records are available going back to 1893. Through 128 years of droughts and floods and everything in between, there was only one year in which a majority of the precipitation fell in the summer months.

It was 2015. California was in the midst of its worst drought on record. And the strongest El Niño on record was forming in the tropical Pacific.

As the summer began, four consecutive years of drought and unusually severe heat put the region on high alert for wildfires and water shortages. Yet the atypical summer rains that would drench Southern California in July and September would result in the quietest fire season in the region in the past decade.

Here’s a look back at the freak wet summer of 2015. It’s a good reminder of the region’s climate variability and raises the question of whether increased summer rainfall would be most helpful in alleviating fire risks in the Southland.

An Active Eastern Pacific Hurricane Season Sets the Stage for a Wet Summer

While monsoonal moisture impacts mountain and desert areas of Southern California in most summers with occasional showers and thunderstorms, significant region-wide summer rain events almost always occur in connection with the remnants of hurricanes that move north from off the coast of Mexico (only one has made landfall in Southern California in historic times, and that was in 1939).

In 2015, the Eastern Pacific experienced its second most active hurricane season on record, no surprise for a year in which El Niño was the strongest on record. The unusually warm ocean temperatures in the Pacific in El Niño years provides fuel for Pacific storms.

There were 26 named storms, 16 hurricanes and 11 major hurricanes.

Of these, two storms – Hurricane Dolores and Hurricane Linda – were responsible for the bulk of the Southland’s unusual summer rain.

Hurricane Dolores

A Category Four monster off the coast of Mexico, Hurricane Dolores weakened quickly as it moved north offshore of the Baja California coast. On July 22, it finally dissipated a few hundred miles west of San Diego.

But since the northeast quadrant of tropical systems always bring the most rainfall and other impacts, weakened Dolores still gave Southern California not only some welcome rain, but even some flood troubles.

San Diego and Los Angeles both set monthly records for July rainfall, at 1.70 inches and 1.30 inches, respectively. Many foothill and mountain areas in San Diego County received more than four inches of rain.

The San Diego River reached 8.9 feet – just below flood stage – a dramatic rise considering the ongoing drought at the time.

And in the Inland Empire, flooding closed roads and washed out bridges.

Rain totals from Hurricane Dolores. Image from the National Hurricane Center

Hurricane Linda

While rainfall from Hurricane Dolores helped freshen up the countryside for a few weeks, the heat of summer quickly dried vegetation, raising fire danger once again.

But September would bring another welcome wet surprise for Southern California, thanks to Hurricane Linda, which peaked in intensity as a Category Three storm off the southern Baja coast before rapidly weakening in the open ocean.

On Sept. 15, 2.39 inches of rainfall fell in Downtown Los Angeles, for the city’s second wettest September day on record (second only to Sept. 25, 1939, when an unnamed tropical system made landfall near Long Beach).

Rain totals in the inches were common throughout the region, and the freak storm even caused the disruptive closure of Highway 91 in Corona, where a 50-yard crack opened up amidst construction efforts.

A student at Cal State Fullerton at the time, I remember sitting in traffic in heavy rain on the alternate route of Highway 60 as I attempted to get to my classes and student job that day.

The most devastating impacts of Hurricane Linda occurred in Utah, where flash flooding wrought by the storm’s remnants left 20 people dead in the worst such disaster in that state’s history.

Observations and Conclusion

Rainfall is usually thought of as almost exclusively a late autumn, winter and early spring phenomenon in Southern California, and for good reason. Almost all of the major storms that have impacted the state have occurred in that timeframe.

But the wet summer of 2015 shows that heavy rain is possible in summer, with both benefits for fire suppression and drawbacks due to flash flooding.

Looking at weather records for Riverside, it is notable that summers with more than two inches of rainfall have often – though not always – occurred amidst broader droughts. Some of these years include 1983, 1977, 1976, 1963 and 1935.

Perhaps this should provide cause for cautious optimism when entering a drought year, since summer rain could provide some support in minimizing fire risks.

The lack of snowpack during summer storms makes these systems less productive for the state’s water supplies, however.

Not surprisingly, summer rainfall brings with it unusually high humidity and dew points. Maximum temperatures tend to be lower, but minimum temperatures tend to be higher and thus more uncomfortable during wetter summers. This is a concern for heat stress in vulnerable populations, especially in coastal areas where air conditioning is less widespread.

Excessive heat and humidity particularly occurs in the days immediately before a summer rainstorm. Most of these storms are hurricane-related, and the sinking air and offshore flow generated by these storms during their approach makes sultry conditions likely in even coastal areas of Southern California.

Finally, the wet summer of 2015 brings to remembrance California’s location on the periphery of a major hurricane region, which is just as active as its Atlantic Basin counterpart. While the cool California ocean current makes hurricanes a gray swan event for the region, even a minor warming of ocean temperatures could make such events more frequent or impactful, with both blessings and curses for the natural environment.

Map of the hyperactive 2015 Eastern Pacific hurricane season. NASA public domain image

What if the Pacific Northwest’s Scorching Heat Wave Had Hit Southern California?

On June 28, 2021, the city of Portland, Oregon, endured one of the most extreme hot temperatures, relative to previous records, observed in any major city on the planet. Photo from Pixabay

In the past two weeks, weather forecasters covering the Pacific Northwest region watched in disbelief as weather models predicted temperatures in the 110s for cities such as Portland, Oregon, and Seattle, Washington. Temperatures that exceeded all-time record highs by 5°F to 10°F, which is extremely rare anywhere in the world.

As the heat wave drew nearer, confidence grew in the models’ accuracy, and weather forecasters began warning of an unprecedented heat event in Oregon, Washington state and British Columbia.

On June 27-28, the dire predictions turned into reality, with Seattle recording 107°F and Portland seeing 115°F. The previous all-time records were 103°F and 107°F, respectively, for these cities.

And in Canada, the nation’s all-time record of 113°F was easily shattered, with temperatures approaching 120°F in interior portions of British Columbia.

At the time of this writing, cooler temperatures have arrived, but not before a region woefully unprepared for hot temperatures (Seattle is the U.S. metro where air conditioning is the least widespread) had experienced one of modern history’s most extreme heat events.

Californians can be thankful that the massive ridge of high pressure that fed the Pacific Northwest heat wave occurred to the north, rather than over the Golden State.

But for a hypothetical case, what would have happened if a heat event of the same magnitude as the 2021 Pacific Northwest scorcher occurred in Southern California?

It Would Be a True World-Record Scorcher

Summer temperatures in portions of the Low Desert and Death Valley are already among the hottest on the planet. So an unprecedented heat wave there could easily result in the hottest temperatures recorded on earth.

Take Palm Springs, which has a record high of 123°F. Add the extra degrees that Portland and Seattle experienced and it would be between 127°F and 131°F there. On the high end of the range, this would be some of the hottest air temperatures ever recorded in a metropolitan area anywhere on the planet.

Even more remote desert spots (i.e., Death Valley or Needles) would approach the hottest possible air temperatures on the planet, well into the 130s!

The Inland Empire would only be slightly cooler, and the offshore flow that accompanied the Pacific Northwest heat wave would ensure that temperatures would reach their full potential. Temperatures between 113°F and 126°F would be the rule across the valleys.

In Downtown Los Angeles, the high might be somewhere between 117°F and 121°F, temperatures considered exceptional even in desert towns such as Las Vegas or Phoenix.

Conditions in beach areas might be more complicated. Even during the Pacific Northwest heat wave, beach towns were considerably cooler, thanks to a persistent marine layer (which ultimately brought an end to the worst of the heat on the evening of June 28).

Astoria, on the Oregon coast, tied its all-time record of 101°F during the Northwest heat wave.

That means, in Southern California, beach towns from San Diego to Venture might be in the upper 100s to low 110s. Certainly not much relief!

A major difference in Astoria was that the extreme heat lasted only one day, rather than three or more for inland areas. So perhaps, if it had occurred in the Southland, there would have been one day of triple digit beach temps, with highs in the 90s on the other days of the event.

Nighttime temperatures in the Pacific Northwest during the heat wave were in the 70s, but typically are in the 50s in summer. For Southern California west of the mountains, summer nights average in the 60s.

So in a comparable heat event, nighttime lows in the 80s would probably be the norm in coastal and valley areas. In the Low Desert, nighttime lows might not dip below 100°F at all! That’s only been known to occur at Death Valley or along a few spots near the Persian Gulf.

No doubt wildfires and power outages would occur in Southern California in such an extreme scenario, compounding the stress on the region and raising risks for many.

Extreme anomalies in air pressure over the Pacific Northwest region during the 2021 heat wave. Higher air pressure in summer translates to hotter temperatures.

Could It Really Happen?

A day in the 120s and 130s across Southern California is a terrifying thought to many. But could such a heat wave really occur?

It might be hard to say for certain, since the Pacific Northwest heat wave would have seemed improbable to even many experts before it happened.

But looking at the experience with other recent mega-heat waves around the world, it seems that the greatest heat anomalies (departure from normal temperatures) occur at more northern latitudes of the Northern Hemisphere.

Thus, while the highest absolute temperatures are still in the world’s deserts, the most unusual heat has occurred in places such as Western Europe in 2003 or Russia in 2010. And going further back in time, the July 1936 Dust Bowl in the U.S. Great Plains and the 1540 heat wave in Europe would provide precedents, and both occurred further north than California.

This might provide some measure of comfort to Southern Californians, since the region is further south and is expected to have smaller temperature increases in global warming scenarios than, say, Arctic or mid-latitude spots.

But Southern California’s mountains allow for offshore flow, which when in place, can easily warm spots west of the mountains to some eyepopping highs, even in winter. With that in mind, a Pacific Northwest-style heat event might well be possible in at least parts of the Southland.

Thankfully, California dodged a bullet in June 2021. Hopefully, such extreme heat never occurs in our region.

Floods, Fires and Hurricanes: A Look at Southern California’s Wacky Weather on the Eve of World War II

A newspaper headline on the November 1938 Arrowhead fire, on display at the San Bernardino County Museum. Photo from April 2021

Today’s Southern Californians have become accustomed to reports of devastating wildfires, while those old enough to remember the 1990s recall periodic massive flooding that left its mark on the Golden State.

Certainly, natural disasters in California, as in many parts of the world, have become more extreme in recent decades.

Yet on the eve of World War II, the region also faced an array of unusual meteorological phenomena. It’s largely been forgotten, but the floods, fires and hurricanes that threatened hearth and home in the late 1930s are important for today’s Californians to look back on, providing perspective on the full array of dangers that the state faces.

Massive Floods Hit the Southland

In 2003, in the aftermath of the most devastating wildfires that Southern California has experienced, former U.S. Representative Jerry Lewis (R-Redlands) called the blazes “the worst crisis I’ve seen in this region since the 1930s flood.”

The statement was widely quoted in local media, but what of the earlier, almost forgotten disaster, that Lewis recalled from his early childhood in the Inland Empire?