Autumn heat wave could break season-level records in California

Unusually hot temperatures are expected to blanket California this week as part of an early-autumn heat wave, forecasters warn, possibly stretching through the weekend.

More than 6 million people in the western U.S. are under heat advisories and watches this week, according to forecasts from the National Weather Service

Down the California coast and across the southwestern U.S., a heat dome could allow temperatures to reach season-high records, AccuWeather meteorologists say. San Francisco, known for having temperate weather most of the year, could see the heat spike in the mid-90s, as a high pressure system traps warmth over a pocket of the western U.S.

“It’s unusual to get temperatures this warm this late in the year, that's why you see these records being threatened," Ashton Robinson Cook, a meteorologist with the National Weather Service told USA TODAY.

Ocean breezes along California that usually allow for cooler weather won't be reaching the shore this week, Robinson Cook said, because the high pressure system, or heat dome, is driving temperatures up so much. Instead of blowing onto land, the heat will keep ocean breeze offshore, he said.

“It won’t be coming in from the ocean at all," Robinson Cook said, explaining how the heat dome will prevent inland flow.

Residents in cities like Los Angeles, Las Vegas and Phoenix will likely feel abnormally hot temperatures through Friday, Robinson Cook warned, and possibly as late as Sunday.

Heat records could be broken in California

A wide strip of the California coast, including San Francisco, was under a heat advisory Monday, warning of high temperatures reaching 95 degrees Fahrenheit. Just inland from the Bay area, the heat could soar to 105 degrees, the National Weather Service said Monday.

San Francisco's heat record for this time of year was set in 1980, when temperatures reached 97 degrees Fahrenheit, according to AccuWeather.

Further north, Robinson Cook pinpointed Ukiah, California, as another city that could break heat records. Throughout the week, Robinson Cook said, Ukiah could reach 103 degrees, surpassing its record of 102.

Los Angeles under excessive heat watch

Temperatures will be scorching hot in southern California, where Los Angeles is under an excessive heat watch through Wednesday evening, with officials warning of temperatures as high as 103 degrees Fahrenheit.

This week's heat dome is "set up over the California area and stretches to the desert southwest," Robinson Cook said.

In California's largest city, the weather service is warning of heat-related health risks, and warned residents to keep out of the sun.

"There is a high risk for dangerous heat illness for anyone, especially for the very young, the very old, those without air conditioning, and those active outdoors," the weather service said Monday.

Like further north, smaller towns in the greater Los Angeles region could also break historical heat records this week, Robinson Cook said.

North of Los Angeles, the desert city of Palmdale could see heat reach 102 degrees Fahrenheit this week, he said, surging past the town's record of 99. In Needles, along the Arizona border, temperatures could reach 109, surpassing that town's record of 108.

'Las Vegas should break a record'

Las Vegas, as well as Phoenix, could shatter heat records for early October.

Even in Las Vegas, which is known for dry, hot conditions, extreme heat this late in the year can be especially harmful, the weather service said Monday.

"Late-season heat is dangerous, because people are fatigued from fighting heat all summer," the weather service said.

In Phoenix, the heat could soar to 113 degrees Fahrenheit, shattering a record of 107 set in 2020, according to AccuWeather.

AccuWeather meteorologists predict Las Vegas could see temperatures rise to 104 degrees Fahrenheit, breaking a record of 103 set in 1978, the outlet said. The weather service has an even hotter outlook, warning temperatures in the greater Las Vegas area could reach as high as 108 degrees Fahrenheit.

“Las Vegas should break a record," Robinson Cook said.

This article originally appeared on USA TODAY: California heat wave could break San Francisco autumn records