Temperatures in the 100s to 120s will be a daily occurrence across much of the state, while warm nighttime lows will provide minimal relief. A strong and abnormally persistent heat dome will kill clouds and keep cooler fog at bay. The heat will also fuel an escalating fire threat; the Thompson Fire in Northern California has already grown to more than 3,000 acres and destroyed structures.
The dangerous heat is projected as far into the future as reliable forecasts are available. All-time records approaching 120 could be threatened as far north as Redding, while Death Valley could approach 130 degrees, the highest temperature reliably measured on the planet.
The weather service has warned that “numerous heat-related deaths and power outages” are possible.
The heat wave comes amid the planet’s hottest year on record, with the last 13 months, including June, hitting record highs. According to science communications agency Climate Central, human-caused climate change has made this week’s heat wave in California at least five times more likely.
The maps below illustrate how severe the heat is that awaits us.
Heat warnings in effect for 70 percent of the state
More than 70 percent of California is under an extreme heat warning. Some of the heat warnings issued by the Weather Service extend seven days into the future, an unprecedented length of time, the San Francisco Chronicle reported.
Cities under extreme heat warnings include Redding, Sacramento, Fresno, Bakersfield, Santa Barbara, Burbank and Palm Springs.
Heat warnings — for slightly less extreme conditions — are in effect for Los Angeles, Santa Maria, San Francisco and other coastal cities, along with parts of the Sierra Nevada. A few spots right on the coast are not included in the warnings.
Temperatures can rise above 130 degrees
The numbers are shocking: Large parts of California will experience temperatures above 110 degrees Celsius in the coming week. Some areas will exceed 120. Only areas along the coast and in the higher mountain ranges will avoid triple digit temperatures.
Death Valley, which holds the record for the highest temperature ever recorded on the planet, has predicted highs of 126, 128, 130, 131, 131 and 133 over the next six days. The world record temperature of 134 was set in 1913, although there are questions about the reliability of that measurement. In 2020 and 2021, it reached 130 degrees, the highest reliably observed temperature in modern records. Last summer, it reached 129.
Heat dome reaches near historic intensity
The heat dome responsible for these extreme temperatures is expected to reach record strength and linger over California and the southwestern United States for seven to 10 days.
“This is the hottest synoptic pattern we’re seeing,” the Weather Service’s Las Vegas office wrote, as record highs are possible.
The heat will not be limited to California, but will also affect much of the Southwest and occasionally the Pacific Northwest.
Research has shown that heat domes like these are getting bigger and more intense due to human-caused climate change.
The Weather Service predicts a flood of record highs and warm lows. Hundreds of records are likely to be broken before the heat wave is over.
Calendar day records will be the most common, but some monthly and even all-time records may be threatened. The number of records set will increase through Thursday and will be most numerous between Friday and early next week.
Some of the all-time records at stake include 121 in Palm Springs on Saturday, 118 in Redding on Saturday and 118 in Las Vegas on Monday.
Extreme heat may continue for another 7 days
The federal government’s HeatRisk Index of 0 to 4 is expected to reach levels 3 and 4, considered large and extreme, each day over the next week in the Central Valley and the deserts.
At these levels, the risk of heat-related illness increases significantly, especially for vulnerable groups such as people who work outdoors, the homeless and the elderly.
While major coastal cities will be largely spared, areas just inland will face several days of dangerous heat.
Jason Samenow contributed to this report.