California braces for triple-digit heat as dangerous weather pattern looms: What to know

LOS ANGELES - Southern California is bracing for summer-like temperatures this week, along with gusty winds that will trigger fire weather concerns for much of the region, according to the National Weather Service. 

"An extended period of hot weather and increased risk for large grass fires Tuesday-Friday away from the coast," the NWS wrote on X. "There will be a moderate risk of heat illness, especially for sensitive individuals, those without air conditioning, and those doing outdoor activities."

According to the latest forecast, highs in the 90s to low 100s are possible for inland and valley areas, with the warmest days expected to be Wednesday and Thursday, peaking on Wednesday.

Here's a look at the latest heat timeline:

Coasts:

Fire Weather

• Timing: Through Tuesday night, peaking with sundowner wind activity during late afternoon and nighttime hours.
• Details: Elevated fire weather conditions due to gusty winds of 35 to 50 mph across the Southwest Santa Barbara coast and adjacent foothills, mainly from Gaviota to San Marcos Pass/Mission Canyon. Humidities falling 15-25% Monday/Tuesday afternoon/evening.
• Impacts: Rapid fire growth possible, especially for grassy areas across Santa Barbara County.

Heat

• Timing: Peaking Tuesday through Thursday
• Details: Minor heat risk concerns, mainly Tuesday through Thursday when high temperatures could reach the upper 80s to lower 90s across the warmest portions of the coastal plain.
• Impacts: Heat exhaustion, heat stroke especially for at-risk populations including the elderly or those without air conditioning, as well as those that will be hiking.

Valleys, Mountains, Deserts:

Fire Weather

• Timing: Sunday through Thursday
• Details: Greatest fire risk will be in the lower mountains, interior valleys, and Antelope Valley, with large grass fires possible. Strongest winds will be through Monday night for the mountains, Antelope Valley, and San Luis Obispo County Interior Valleys. From Tuesday through Friday, onshore wind gusts of 20 to 40 mph across the interior is expected each afternoon and evening, with the strongest in the Antelope Valley, Highway 14 corridor, and San Luis Obispo County interior valleys.
• Impacts: Rapid and large fire growth possible for fine fuels, especially grasses.

Heat

• Timing: Peaking Tuesday through Friday
• Details: Moderate heat risk concerns, mainly Tuesday through Friday when high temperatures could reach the upper 90s to lower 100s across the warmest valleys. Hottest days this week likely to be Wednesday and Thursday.
• Impacts: Heat exhaustion and heat stroke, especially for at-risk populations including the elderly or those without air conditioning, as well as those that will be hiking.

Max Temperatures:

According to the NWS, the coasts will warm 3 to 6 degrees. Most max temps will end up 4 to 8 degrees above normal, the NWS said. 

Most of San Luis Obispo and Santa Barbara counties will warm just 1 to 2 degrees, but Ventura and LA counties will see another 4 to 8 degrees of warming due to the offshore flow.

"Max temps across the coasts will be in the 70s except the interior portions of the LA/VTA coasts where lower to mid-80s will be common," the NWS said. 

"The valleys will see max temps from 95 to 103 degrees, 15 to 20 degrees above normal," according to the National Weather Service. "... Warmer than normal highs and lows will combine to bring moderately dangerous heat conditions to the valleys and lower mountain elevations."

Weather Alerts:

A heat advisory will take effect at 11 a.m. Tuesday in the Santa Monica Mountains Recreational Area, Calabasas, Agoura Hills and the San Fernando Valley, continuing until 9 p.m. Thursday.

A separate heat advisory will be in place from 11 a.m. Wednesday until 9 p.m. Thursday for the Santa Clarita Valley, San Gabriel Valley and Los Angeles County coastal area stretching to downtown L.A.

All the affected areas could see triple-digit heat, forecasters warned.

Cooler Weather:

Cooler temperatures will arrive on Saturday, with coastal low clouds likely into Memorial Day weekend. 

"The big news will be the temps: look for 5 to 10 locally 12 degrees across the area. The biggest cooling will occur in the LA/VTA valleys. Max temps will drop to a few degrees either side of normal," the NWS said. 

This will make temperatures return to "a few degrees either side of normal," the NWS said, followed by a few degrees of warming on Sunday.

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