Forecasters Warn L.A. of a 'Very Dangerous' Heat Wave Lasting Up to Two Weeks

An extreme heat watch covers Orange County Friday through Oct. 7, and L.A. forecasters say heat advisories here are very likely.

A "very dangerous" heat wave could push the hottest Los Angeles valleys into triple digits Friday and hang on for two weeks, the National Weather Service said.

The warning came from the weather service's Los Angeles/Oxnard office in its forecast discussion early Wednesday, Sept. 30. It describes a heat wave of 10 to 14 days. It also says every long-range model the office checks, "both traditional and AI-enabled," keeps the heat going until at least Oct. 13.

Here's what a lot of people searching "extreme heat watch" this morning want to know. Los Angeles County isn't under one.

As of Wednesday morning, the only heat alert in all of California came from the weather service's San Diego office. The Orange County Register reported that the office issued an extreme heat watch at 3:05 a.m. It starts at 10 a.m. Friday, Oct. 2. It ends at 9 p.m. Wednesday, Oct. 7.

That watch covers the Orange County coast, inland Orange County, the Santa Ana Mountains and foothills, the San Bernardino and Riverside County valleys, and coastal and inland San Diego County. Highs should run around 90 near the beach, the Register reported. The valleys are forecast to reach the upper 90s, and up to 108 on the worst days.

The nights won't bring much relief. The San Diego office expects lows from the coast into the western valleys to stay in the lower to mid 70s through the weekend and into next week, according to the Register. "Heat related illnesses increase significantly during extreme heat events," the weather service warned.

The difference between the two counties this morning is paperwork, not temperature.

The Oxnard office's own forecast for L.A. climbs day by day. On Thursday, Oct. 1, it expects coastal highs mostly in the 80s. The valleys should reach the 90s, about 8 degrees above normal. The San Fernando and San Gabriel valleys are forecast to warm 4 to 6 degrees from the day before.

Friday gets worse. The warmest valleys are forecast to top 100 degrees. Interior coastal neighborhoods should reach the lower 90s, and even the beaches are expected to hit the lower 80s. The weather service puts the odds at 30% that Friday runs another 3 degrees hotter than that. Saturday, Oct. 3, is forecast to be hotter still.

That's the stretch when most people will be outside running errands, at a game or at the beach, and it's why the Oxnard office didn't hedge much about what comes next. "It is very likely heat advisories will be issued for most of the LA/VTA county cst/vlys," the discussion says, meaning most of the coast and valleys in Los Angeles and Ventura counties.

The basics for getting through it come from UC Irvine's environmental health and safety office. A person working in the heat can sweat out 2 to 3 gallons a day. So the office recommends drinking 3 to 4 cups of water every hour and cutting back on alcohol and caffeine, which both dry you out. If you feel nauseated, dizzy, weak or unusually tired, get into the shade and rest, and get medical help if it doesn't pass.

Keep an eye on the people around you, too.

Los Angeles County lists its cooling centers at ready.lacounty.gov/heat. Orange County posts its list at ocgov.com/cooling-centers, and Riverside County posts its list at capriverside.org/cool-centers. The next move is Oxnard's, and its forecasters have already said which way they're leaning.

Source: ocregister.com, retrieved September 30, 2026.