“This is an extraordinary heat event that we are experiencing, and consumer efforts to lean in and reduce their energy use after 4 p.m. are absolutely critical,” said Elliot Mainzer, President and CEO. of California ISO, in a press release. The agency, which declared an energy emergency alert, forecast historically high demand of 51,033 megawatts on Tuesday afternoon, surpassing its previous record high of 50,270 megawatts on July 24, 2004.
The ISO is urging residents to “pre-cool” their homes to 72 degrees on Tuesday and Wednesday mornings, then turn the thermostat up to 78 degrees during peak hours between 5 p.m. and 9 p.m. He called for such cuts for seven consecutive days.
The heat is historic in both its duration and intensity, as evidenced by the long-standing monthly and all-time highs that continue to be broken. In Sacramento, the downtown district reached 113 degrees on Monday, just one degree below the all-time high set on July 17, 1975 and four degrees higher than the previous high in September. The archives there date back to 1877.
On Tuesday afternoon, Sacramento is expected to hit 115 degrees, which would be both a monthly and all-time high as well as the 11th time in the past 145 years that the city has hit 112 degrees or higher. Fairfield, Calif., on the northeast side of the Bay Area, set an all-time high of 117 degrees on Monday.
A whopping 42 million Americans are under excessive heat warnings, including across most of California, northeastern Arizona and adjacent southern Nevada. The Great Basin, southern Idaho and western Utah are subject to heat advisories.
“Extreme heat will greatly increase the potential for heat-related illnesses, especially for those who work or participate in outdoor activities,” the National Weather Service wrote. “[There is a] very high risk of heat stress or illness for the general population.
Maximiliano Herrera, a world weather historian, called it “the worst September heat wave in western United States history.” on Twitter during the weekend.
Excessive heat also fuels the risk of rapid fires.
Red flag warnings — indicating dangerous fire weather — encapsulate all of Montana in addition to northern Idaho, much of Oregon and northern and eastern Washington.
A number of large wildfires have erupted over the past week in California, Oregon, Idaho and Montana. The rapid fire at the factory, which broke out in northern California on Friday, killed two people and three wounded. On Monday, two people died and another was injured in the Fairview Fire, which started near the town of Hemet, about 75 miles southeast of Los Angeles in Riverside County.
Hottest weather still possible for some Tuesday
The heat will reach a searing crescendo on Tuesday as a stagnant high-pressure “heat dome” peaks overhead. It pushed back clouds and rain and diverted the jet stream north towards Canada. Below, descending air and relentless sunshine provide some of the hottest weather ever seen in the Golden State.
Outside of the deserts, the worst was concentrated in the Central Valley of California. The National Weather Service explicitly predicts Sacramento will hit an all-time high of 115 degrees on Tuesday. Along with being an all-time high, that temperature would also erase what until Monday had been Sacramento’s monthly record for September of 109 degrees.
Some places in the Central Valley could approach 118 degrees.
“It still looks like the ongoing record-breaking heat wave will peak today, but dangerous heat likely persist until the end of the week”, wrote the weather service office in Sacramento on Tuesday.
The heat traces the backbone of California to the Bay Area and Southern California. San Francisco airport is expected to reach 99 degrees on Tuesday. Although incredibly hot, September 6, 2020 was three degrees warmer. Either way, it’s still two dozen degrees warmer than the average 75.
Los Angeles will spend the next few days in the mid to high 80s, but should peak around 90 on Friday. Keep in mind this is at the airport – a few miles inland the highs will hover around 100-105 degrees.
Death Valley, California has hit 124 degrees three times in the past five days. He could flirt with 126 on Tuesday, which would tie a world record for September.
The heat also spread eastward, bringing hot weather to Denver, with records in the 90s above nearly 100 scheduled until Thursday. Salt Lake City — which set a September record of 104 on Monday — will continue to hover in the low 100s.
The heat will begin to gradually subside on Thursday. Nearer-average temperatures will return to much of California over the weekend, although temperatures will remain somewhat above normal over the Pacific Northwest and northern Rockies.
At that time, the humidity of Hurricane Kay in the Pacific The southwestern Baja Peninsula could begin to float north, lowering temperatures and possibly bringing beneficial rainfall to southern California and even farther north. However, its specific effects on the region are very uncertain and it could also increase the dry lightning potential which could increase the risk of fire.
Link to climate change
Even if oppressive heat events are not caused by climate change, human influence on our atmosphere makes them more frequent, intense and prolonged. It propels already high-end events into record territory.
Breaking records by wide margins, the heat wave bears the nuances of the unprecedented events that set fire to the Pacific Northwest in June 2021 and the UK Brittany in Julywhich scientists have concluded would have been virtually impossible without human-induced climate change.
In the United States, in the past week, more than 1,141 hot weather records have been set in the United States compared to only 36 cold records. If climate change were not a factor, these extremes would roughly balance each other out.
From California to Montana, hundreds of heat records have been set since August 30, and dozens more are in danger over the next few days.
In addition to calendar day records, several locations have set monthly records and even all-time records (the hottest temperature observed in a month). Here we highlight some of the most significant:
- Downtown Sacramento set a September record of 113 on Monday, just one degree off its all-time high of 114 set on July 17, 1925. Stockton (112), Vacaville (115) and Marysville (113) also set records in September in the Central Valley of California.
- Fairfield, Calif., about 40 miles northeast of San Francisco, set an all-time high of 117 degrees on Monday – three degrees above the previous record. Livermore set a historic record of 116.
- Salt Lake City broke its previous September record three times in the past week. He knocked 104 on monday, 103 Saturday and 102 Thursday. The previous monthly high was 100. It has hit at least 100 five times this month. Before 2022, it only did it three times during September dating from 1928.
- Reno, Nevada, set a September record of 104 on Sunday, after tying the previous monthly record of 102 on Friday.
- San Diego tied its hottest low temperature on record on Sunday, falling to just 78 degrees.
- Burbank, Calif., tied its all-time hottest low on Sunday, falling to just 82 degrees. Wednesday he set a record temperature in August of 112.
- Las Vegas on Sunday set a record low temperature of 87C in September.
- Casper, Wyo., set a September record of 100 on Sunday.
- On Saturday, Death Valley’s low temperature of 102 degrees equaled the highest minimum temperature on record globally in September. Death Valley exceeded 120 degrees for seven consecutive days, setting records of 123 calendar days on Wednesday, 124 on Thursday, 124 on Friday, 122 on Saturday and 124 on Sunday. He established a new september record for most days reaching at least 120.
- Many Mountain West locations set September records on Saturday, including Great Falls (102), Bozeman (10o) and Butte (96) in Montana and Pocatello (102) and Idaho Falls (99) in Idaho.
- Heat even erupted in western Canada on Friday, where the village of Lytton set a September record for British Columbia of 103.3 degrees (39.6 Celsius).
- Fresno, Calif., tied its September record on Friday, soaring to 111 degrees.
- Redmond, Oregon, on Friday set a September record of 106.