SACRAMENTO, Calif. — Scorching hot temperatures are on the way to California, with a record-breaking heat wave poised to sweep the state, according to the National Weather Service.

The National Weather Service has issued a heat advisory for most of California.

Here’s when and where to expect the hottest temperatures:

When will highest temperatures hit?

Starting Friday, high temperatures are expected to surge across California, which could potentially near or break records, according to the National Weather Service.

“By Friday and Saturday, daily high temperatures will begin pushing record levels for this time of the year across parts of the western (United States),” the weather agency said on X.

Which areas of California are under heat warnings?

Heat advisories are in effect across much of California, including the Central Valley, Bay Area and parts of Northern and Southern California, from 11 a.m. Friday to 11 p.m. Saturday.

“A heat advisory is issued for dangerous heat conditions that are not expected to reach warning criteria,” the National Weather Service said. “Consider postponing or rescheduling outdoor activities, especially during the heat of the day.”

The weather service also issued extreme heat watches for much of the Sacramento Valley, including Sacramento and Modesto, as well as Fresno, Merced and the rest of the San Joaquin Valley.

During extreme heat watches, the National Weather Service said to “suspend all major outdoor activities.”

“If you do not have air conditioning, locate the nearest cooling shelter or discuss staying with nearby family or friends who have air conditioning,” the weather agency said.

How hot will it get?

Much of California is expected to face elevated heat risks from Friday through Saturday, the weather service said, with daytime high temperatures possibly exceeding 100 degrees.

California residents can expect dangerously hot conditions with high temperatures ranging from 99 to 109 degrees and widespread major heat risks, the weather agency said on X.

The city of Redding is expected to see the highest temperatures — up to 109 degrees — on Friday, May 30.

What’s the risk of health issues during summer heat wave?

Starting Friday, most of California’s heat risk will be major, the weather service said.

The heat risk scale provides a forecast that shows the likelihood of heat-related problems occurring.

The scale calculates how hot it is compared to normal, how long the heat lasts, and whether it’s likely to cause health issues based on data from the U.S. Centers for Disease Control and Prevention.

It ranges from 0, meaning there’s little or no heat risk, to 4, indicating an extreme heat risk.

The heat risk is projected to be 3 on Friday, indicating a major heat risk.

According to the weather service, major heat risk “affects anyone without effective cooling and/or adequate hydration.”

“If you must be outside, be sure to drink plenty of water and take frequent breaks in the shade,” the weather agency said. “Stay in a cool place, especially during the heat of the day and evening.”

Who’s most at risk in California?

Vulnerable individuals include those who are pregnant, newborns, children, older adults and those with a chronic illness. These groups are more at risk due to age and conditions that make it difficult to regulate high temperatures.

“Drink plenty of fluids, stay in an air-conditioned room, stay out of the sun, and check up on relatives and neighbors,” the weather service said in its extreme heat watch.

“Do not leave young children and pets in unattended vehicles,” the weather service warned. “Car interiors will reach lethal temperatures in a matter of minutes.”

What’s in store for California this summer?

The National Oceanic and Atmospheric Administration’s Climate Prediction Center is forecasting higher-than-usual temperatures across much of the country over the summer — including California.

“For (June through August) 2025, we are forecasting 50% to 60% chances of above-normal temperatures for the northern and eastern parts of California, with 40% to 50% chances along the southern coast,” the agency previously told The Sacramento Bee via email.

This means summer “temperatures are likely to be above normal for much of the state” in 2025, the weather agency said.

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