Numerous locations in California experienced their hottest September day on record Sunday. A few spots saw their highest temperatures ever observed in any month.
Woodland Hills, just 20 miles from downtown Los Angeles, soared to 121 degrees, the highest temperature ever observed in Los Angeles County. Chino, 32 miles east of Los Angeles, also hit 121 degrees. Both the Chino and Woodland Hills marks were the highest ever recorded west of the mountains in Southern California.
Farther north, the mercury in San Luis Obispo, just 10 miles from the Pacific Ocean, reached a sweltering 120 degrees. This may be the highest temperature ever measured so close to the ocean in the Americas. Even downtown San Francisco touched 100 degrees, breaking a record that stood for more than a century.
The blistering heat helped fuel a serious wildfire situation Saturday when the Creek Fire in the Sierra National Forest erupted, about 290 miles north of Los Angeles. The blaze was first detected Friday night and rapidly grew to at least 45,500 acres by Sunday afternoon.
That fire trapped about 1,000 people near Mammoth Pool reservoir as flames crossed the San Joaquin River, including about 150 people who became stranded at a boat launch, the Associated Press reported.
According to the AP, 200 people were rescued from the Mammoth Pool Campground by military helicopters. Two of them were severely injured, 10 had “moderate injuries” and others had minor or no injuries. According to the California Air National Guard, this was the largest wildfire-related air evacuation in recent memory.
The Fresno Bee reported that at one point, people trapped by the flames were told to jump in the water as a last resort should the flames get too close. However, Sierra National Forest officials said the fire burned around the reservoir and the evacuations took place because the blaze blocked evacuation routes.
The Fresno County Sheriff’s Office ordered new evacuations Sunday morning as the fire continued to grow.
The Creek Fire sent smoke, embers and fine particles 45,000 feet in the air Saturday and Sunday, forming a pyrocumulonimbus cloud. Such clouds, which look like explosions from a distance, are fire-driven weather systems. The one seen Saturday was causing lightning to strike areas downwind along with erratic and gusty surface winds. Ash fell more than 10 miles away from the fire.
Fires this weekend are what are known as plume-dominated blazes, which occur when the environment is favorable for the upward billowing of smoke and vertical transfer of heat.
Plume-dominated fires can frequently become firestorms, taking on the structure of a thunderstorm because of their incredible vertical release of heat. Extreme fire behavior, as has been seen with the Creek Fire, is often a characteristic of plume-dominated fires.
The Creek Fire appeared to produce multiple fire tornadoes based on Doppler radar data, which revealed vortices inside the fire and smoke plume that matched the size and shape of tornadoes.
A change of wind speed and direction with height known as wind shear caused the smoke plume to rotate. In an unusual turn of events, the smoke plume’s updraft also appeared to repeatedly split, with pairs of spinning rotations repeatedly forming and drifting away from one another.
The Loyalton Fire in Lassen County, Calif., produced five or more fire tornadoes barely three weeks ago, prompting the National Weather Service to issue a first-of-its-kind fire tornado warning.
In addition to the Creek Fire, firefighters are still battling the second-, third- and fourth-largest fires in state history that erupted during a mid-August heat wave and unusual thunderstorms north of San Francisco. Although those fires are better contained, the heat, dry weather and shifting, strong offshore winds are causing an uptick in their activity.
Since Aug. 15, the state has seen more than 1.6 million acres burned and 900 new fires started, along with eight deaths and nearly 3,300 destroyed structures. In an average California fire season to date, about 310,000 acres are burned, according to Cal Fire, the state firefighting agency.
Daniel Swain, a climate researcher at the University of California at Los Angeles, said the state may set a record for the “most acres burned in the modern era” as soon as Monday.
Firefighting operations will continue to be extremely challenging because of the triple-digit heat and extremely low humidity levels, according to the Weather Service.
Forecasters are monitoring two periods for strong, desiccating offshore winds to pick up in strength early this week. The first looks as though it could take place Sunday night through Monday evening, with the next taking shape as a rare early-season Santa Ana wind event in Southern California on Tuesday into Wednesday.
The Weather Service’s forecast office in Los Angeles is predicting “elevated to critical fire danger” through Wednesday.
The Weather Service office in Los Angeles described Sunday’s heat as “kiln-like,” predicting a “dangerous to potentially deadly” extreme heat event.
Ninety-nine percent of the state’s population was under an excessive-heat warning or heat advisory, according to the Weather Service office in Sacramento.
In a sign of the heat to come, temperatures did not drop below the 90s on Saturday night and into early Sunday in some locations from the San Fernando Valley to parts of L.A. County. Two temperature stations in the L.A. area were still hovering above the century mark at 3:02 a.m. local time, the Weather Service said.
High temperatures in Southern California on Sunday ranged from 105 to 115 degrees near the coast to up to 120 degrees in inland areas, which would edge past all-time-high temperature records in some locations.
Some noteworthy temperature records that have already fallen include:
- Burbank, Calif., tied its all-time-high temperature record of 114 degrees on both Saturday and Sunday.
- Palm Springs hit 122 degrees Saturday, breaking its previous September record from 1950.
- Death Valley, Calif., set a September record with a high of 125 degrees, beating the old record of 123, set in 1996. This comes just two weeks after reaching 130 degrees, an August record, and the highest temperature observed globally since at least 1931.
- The 121-degree temperature recorded in Woodland Hills, Calif., on Sunday was both the highest temperature on record there and the highest temperature seen anywhere in Los Angeles, Ventura, Santa Barbara and San Luis Obispo counties, the Weather Service said.
The massive heat dome sprawled over western North America established September records from Mexico to the Colorado Rockies. Mexicali, Mexico, soared to 121.1 degrees Saturday, the country’s hottest temperature ever observed during the month. Denver hit 101 degrees Saturday, its highest September temperature and the latest on record it has crossed the century mark. Nearby Boulder hit 99 degrees both Saturday and Sunday, its hottest temperature so late in the year. On Tuesday, Denver and Boulder are expecting snow.
La Junta, Colo., about 60 miles southeast of Pueblo, registered a high of 108 degrees, a state record for the month of September.
Temperatures are forecast to cool some by Tuesday but to remain above normal in most of California for much of the week.
Studies show human-caused climate change is tilting the odds in favor of more frequent, severe and longer-lasting heat waves, as well as larger wildfires throughout large parts of the West. Research published last month, for example, shows climate change is tied to more frequent occurrences of extreme-fire-risk days in parts of California during the fall. (Meteorologists define the fall as beginning Sept. 1.)
Michael Wehner, who researches extreme weather events at Lawrence Berkeley National Laboratory, estimates “climate change has caused extreme heat waves to be 3 to 4 degrees Fahrenheit warmer in California.” These trends “will continue as the planet continues to warm,” he said in an email, noting the amount of warming will depend on future greenhouse gas emissions.
The heat wave has prompted warnings from the operator of California’s electricity grid that rolling blackouts may need to be instituted during times of peak power use, and it has asked residents to take steps to reduce electricity use during times of peak demand. A “Stage 2 warning” was issued Saturday and Sunday, indicating all efforts at outage mitigation had been taken, but it was not followed by outages.
The California ISO declared a “Flex Alert” on Sunday, calling for reduced electricity use between 3 p.m. and 9 p.m. local time.
The state utility PG&E has also warned it may institute rolling outages if winds get too strong early this week, because its power infrastructure has been blamed for sparking some of the state’s largest and deadliest blazes in recent years.
Extreme heat has been the top weather-related killer in the United States during the past 30 years, and combined with poor air quality from nearby fires as well as the coronavirus pandemic, the health threat is particularly acute. Air conditioning provides the best protection from excessive heat, but because of the possibility of exposure to the virus at cooling shelters, the pandemic may keep people who lack air conditioning at home.
Jason Samenow, Scott Wilson and Matthew Cappucci contributed to this report.