'Dangerous' heat wave expected to break records across California this weekend

Karen Garcia, Los Angeles Times on May 30, 2025

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LOS ANGELES – A heat wave is set to inflict misery on nearly the entire length of California starting Friday.

Triple-digit heat is expected up and down the state, pushing record-level temperatures for the first time this year. Heat advisories are in effect for large swaths of the region over the course of the two-day heat wave, with possible thunderstorms near the border with Nevada in the Reno area.

Look for advisories across Northern and Southern California, including the Bay Area, Central Valley and Central Coast.

On Friday, temperatures in Southern California are expected to range from eight to 16 degrees above normal, with highs in the 90s to just above 100 degrees across the valleys, lower mountains and deserts, according to the National Weather Service's Oxnard office.

"By Friday, levels reach 'Major (Red)' in many areas, which means heat affects anyone without effective cooling and/or adequate hydration," the National Weather Service posted on X.

In Los Angeles County, the Public Health Department issued a heat advisory for residents in the western and eastern areas of the San Fernando Valley, as well as the Santa Clarita Valley, warning of the high risk of heat-related illness for sensitive populations — adults who are 65 and older, as well as children and those with chronic illnesses. Forecasters are expecting temperatures to reach as high as 100 degrees.

To the north, from the Shasta Lake area to the Sacramento Valley, "dangerously hot conditions" are expected, with temperatures from 99 to 107 degrees, according to the National Weather Service's Sacramento office. And the Mendocino area could see sizzling temperatures of 102 to 105.

Along the Central Coast, the thermometer could hit 100, with intense heat anticipated in the city of Paso Robles. Locals and travelers headed to the Cuyama Valley, southern Salinas Valley or the mountain and valley areas of San Luis Obispo County are being warned of the triple-digit heat.

Temperatures as high as 106 are forecast for a portion of Central California including Merced, Madera, the San Joaquin Valley, Fresno, the Yosemite Valley and the Sierra Foothills.

An extreme heat warning is also in effect for Death Valley, where temperatures are expected to exceed 115 degrees.

The National Weather Service in Reno has issued a fire weather watch from Saturday morning through Sunday evening due to gusty winds, low humidity and the chance of dry lightning. There is a 10% to 15% chance of isolated dry thunderstorms with gusty, erratic winds primarily in the Sierra.

Starting Saturday, temperatures across California are expected to begin to trend downward, with the largest drop in temperatures occurring in Southern California south of Point Conception, forecasters say. There is also a slight chance, about 10% to 15%, of precipitation on Saturday afternoon in the San Gabriel Mountains.

Also Saturday, Tropical Storm Alvin should be nearing the southern tip of the Baja coast, funneling tropical moisture into San Diego and other parts of Southern California. South of Point Conception, there will be a 10% to 20% chance of showers through Sunday night, forecasters say.

How to protect yourself during a heat wave

For residents living in areas with general to extreme heat advisories, health officials advise you to:

•Drink plenty of fluids.

•If possible, stay in air-conditioned rooms.

•Check on relatives and neighbors.

•If you have to be outside, wear lightweight and loose-fitting clothing and a hat, and use an umbrella.

•Avoid going out during the hottest hours of the day. Stay in shaded areas as much as possible.

•Never leave pets or children alone in a car. Cars get very hot inside, even with the windows cracked or open, officials said.

If you don't have access to air conditioning or a cool environment, there are free cooling centers, splash pads and community pools in Los Angeles County. You can find which cooling centers are near you by checking the Find Relief From the Heat section of the Ready L.A. County Website.

Public health officials say heat-related illnesses, such as exhaustion and heatstroke, increase significantly during extreme heat.

Symptoms of heat-related illness include vomiting, dizziness, confusion, and hot, red, dry or damp skin. If you see or experience any of these symptoms, move to a cool place and call 9-1-1.