Los Angeles County faces ’96 hours of hot temperatures’ in heat wave, forecaster warns

Health officials issued a heat alert for Los Angeles County’s inland valleys Monday, warning that a multiday heat wave expected for Southern California this week will put the community’s most vulnerable residents at risk.

Temperatures aren’t expected to be quite as blistering as they were during a heat wave that shattered records two weekends ago, but the one expected this week will last longer and reach from the San Gabriel Valley and high desert to the coast, the National Weather Service said.

“It’s not going to cool off at night. Just 96 hours of hot temperatures,” warned meteorologist Andrew Rorke. “If you can survive to the weekend you might get a little relief.”

Monday could be up to 8 degrees warmer than it was Sunday, Rorke said. It was expected to be 92 degrees in downtown Los Angeles and 105 degrees in Woodland Hills. The heat wave will peak Tuesday and Wednesday when temperatures will hit 94 each day downtown and 107 in Woodland Hills, Rorke said.

This week’s heat wave isn’t expected to cause any major outages, according to Marty Adams, chief operating officer for the Los Angeles Department of Water and Power.

Adams said the DWP is making sure the city has adequate power supplies and will balance electricity going to different neighborhoods. That way, no one area will be overwhelmed, or at least that’s the plan.

The DWP is most closely monitoring Mid-City, where the power grid was worst hit during the extreme heat wave that gripped the city earlier this month. Department staff are working 12-hour days there, Adams said, fixing potential weak links in the circuitry.

Usually, the L.A. power grid cools down overnight, giving the equipment some rest, Adams said. But when there’s a heat wave, the grid can become overwhelmed without that reprieve — much like how an extension cord is hot to the touch when it’s been used heavily — and malfunction.

DWP customers can help prevent that overload by using less electricity at peak times, from 2 to 9 p.m, Adams said. That’s especially important during a heat wave, when people are using more energy than usual to air-condition their homes.

“Don’t do laundry, don’t use certain appliances if you don’t have to,” Adams said. And keep your thermostat at 78 degrees, if you can bear it, he added.

Also, on Monday, the California Independent System Operator, which runs the electrical grid and shares responsibilities for preventing blackouts and brownouts, issued flex alerts or Tuesday and Wednesday, between the hours of 5 p.m. and 9 p.m. During those periods, consumers are urged to voluntarily scale back their power usage.

The Los Angeles County Department of Public Health issued a heat alert Monday and Tuesday for residents in the Antelope, Santa Clarita, San Fernando and San Gabriel valleys and Pomona. Downtown Los Angeles was included in Tuesday’s heat alert.

“When temperatures are high, even a few hours of exertion may cause severe dehydration, heat cramps, heat exhaustion and heatstroke. Others who are frail or have chronic health conditions may develop serious health problems leading to death if they are exposed to high temperatures over several days,” said the county’s interim health officer, Jeffrey Gunzenhauser, in a statement. “Thus, it is critically important to never leave children, elderly people or pets unattended in homes with no air conditioning and particularly in vehicles, even if the windows are ‘cracked’ or open, as temperatures inside can quickly rise to life-threatening levels.”

A list of cooling centers is available here.

Not only will it be hot with little relief overnight, but the air will be dry and windy inland, which sucks moisture out of any vegetation in the area and primes the landscape for a fast-moving brush fire.

“It’s just piling on the bad news,” Rorke said.

Much of Los Angeles County will likely be above 80 degrees until at after midnight, he said.

The winds that will be posing fire dangers inland will be absent along the coast, which ironically might make it a worse place to be this week because few coastal residents have air conditioning, Rorke said.

“The sea breeze will be nonexistent,” he said.

A 1- or 2-degree dip in the heat is expected Thursday, but temperatures won’t noticeably begin to decrease until Friday, Rorke said. A marine layer could return to the region by the weekend.

On top of L.A. County’s heat alert, the National Weather Service issued its own heat warning from Tuesday through Thursday for Kern, Santa Barbara, Ventura, San Bernardino, Riverside, Orange and San Diego counties.

joseph.serna@latimes.com

For breaking California news, follow @JosephSerna on Twitter.

UPDATES:

2:10 p.m.: This article was updated with details about two upcoming flex alerts from Cal-ISO.

12:25 p.m.: This article was updated with comments from Adams.

This article was originally published at 6:55 a.m.