As Southern California’s worst heat wave of the year intensifies and expands across the region Thursday, officials warn the next few days could bring record-breaking high — and low — temperatures.
Widespread heat advisories have been issued across California and the U.S. Southwest, even encompassing much of the often-spared coastline. While daytime temperatures in the high 90s and triple digits could set records that will exacerbate health and fire concerns, climate scientists warn it’s the limited overnight cooling that might be the biggest concern.
“The entire L.A. Basin, even downtown L.A., [is] not getting below the low 70s,” Daniel Swain, a UCLA climate scientist, said in a briefing this week. Parts of the San Gabriel Valley will remain above 80 degrees at night, and much of the Palos Verdes peninsula won’t fall below 70, according to the National Weather Service.
Phoenix is not forecast to drop below 90 degrees.
“Those overnight minimum temperatures will set records,” Swain said. “We don’t talk about them as much, but they’re hugely consequential from a human health and, in particular, wildfire perspective.”
An extreme heat warning is in place for much of Los Angeles, Ventura, Santa Barbara and San Luis Obispo, warning of “dangerously hot conditions” through at least Saturday. Temperatures Thursday are expected to hover in the mid- to high 90s inland from the coast, and somewhere between 100 and 109 degrees in the valleys, lower mountains and some high deserts. In the Mojave Desert and Coachella Valley, temperatures will climb above 110 degrees.
“This dangerous level of heat will pose a threat to anyone without effective cooling and adequate hydration,” the weather service’s Weather Prediction Center warned. “Highs into the 90s more broadly across the West will still pose a threat to anyone more sensitive to heat or engaging in strenuous outdoor activities.”
In Woodland Hills, a group of mothers on Thursday morning focused on finding a way to keep their toddlers occupied — and safe — in the intensifying heat, as temperatures climbed toward 100 degrees.
“The mixture of heat and toddlers is terrible,” said Celina Nelley, 30, as she sought refuge on a shaded bench at the Topanga Village. “It’s either stay home and do screen time or go outside.”
Her “moms group” had brought their young children to the mall’s outdoor water fountain and climbing gym, but Nelley worried there was not enough shade.
“We need misters and shade,” said Carolla Aguirre, 33, as she handed a crying boy a packet of fruit. Another mom, Natala Jones, 31, said she was noticing that the heat was causing a lot of acting out — both by adults and children.
“People get more aggressive when they drive,” Jones said. “I get more aggressive and in a bad mood. Everyone is in a bad mood!”
Even as some of their kids seemed unfazed by the heat, running around together, Nelley said she wouldn’t last long: “An hour and half tops, and I’m outta here.”
Though Thursday and Friday are expected to be the hottest days in the Southland, temperatures will remain elevated through early next week. Woodland Hills is forecast to top out at 107 on Thursday and downtown Los Angeles may hit 97. It’s forecast to hit 101 degrees in Pasadena.
“The multi-day period of extreme heat ... will also impact and worsen air quality, and smog will reach unsafe levels in many parts of the city,” L.A. emergency officials warned Thursday. “It’s very important to be proactive and make sure you and your community have a plan to stay safe during extreme heat.”
Compounding those safety concerns, officials have warned the heat wave could foster an environment ripe for fast-moving wildfires. A red flag warning is in effect for the Los Angeles and Ventura County mountains and foothills through Saturday night.
“If fire ignition occurs, conditions are favorable for extreme fire behavior and rapid fire growth, which could threaten life and property,” the red flag warnings said.
The dry, hot weather coupled with an unstable atmosphere — that could bring some weekend thunderstorms — is a recipe for dramatic fire growth, officials warn. It’s particularly a concern in Southern California, where back-to-back wet years increased vegetation growth before this year’s dismal rainy season.
“We have the legacy of this wet-to-dry whiplash event,” Swain said. “There’s literally more biomass, more potential fuel, for the fires to burn.”
The hot weather could be accompanied by some monsoonal thunderstorms in the mountains and deserts by the weekend, which could further elevate fire concerns given the chance for lightning. The storms, if they materialize, may also create localized flooding, destructive winds and debris flows, especially in recent burn scars.