A dangerous, multiday heat wave descended on much of California and the U.S. Southwest this week, with near-record temperatures expected through the weekend and officials warning of elevated wildfire risk and serious health threats.
The National Weather Service issued an extreme heat warning for Southern California starting Wednesday, with downtown Los Angeles forecast to reach 97 degrees Friday and valleys to the north bracing for temperatures as high as 108 degrees. Desert areas including Palm Springs will see even hotter conditions.
In Arizona, the peak of the heat wave will hit Thursday and Friday, with temperatures possibly reaching 110 degrees in the southern and western parts of the state. Similar temperatures were expected in Las Vegas. Nearly-always-hot Death Valley could see a severe 120 degrees, the weather service said — 14 degrees shy of its record high of 134 degrees set in 1913.
California Gov. Gavin Newsom ordered state firefighting resources deployed to areas where blazes could ignite as red flag warnings signaling elevated wildfire danger were issued across Los Angeles, Ventura, Santa Barbara and San Luis Obispo counties until Saturday.
"If you live in a high fire danger area in the mountains or foothills, review your evacuation plans and route and stay tuned to your local emergency officials," the weather service said.
The state has sent 10 fire engines and multiple firefighting teams to Los Angeles County to assist local agencies if blazes break out.
"By prepositioning firefighting crews, equipment, and other resources in high-risk areas, we can respond faster and more effectively when needed," said Nancy Ward, director of the Governor's Office of Emergency Services.
California's largest blaze this year, the Gifford Fire, was at 95% containment Wednesday after charring nearly 206 square miles of San Luis Obispo and Santa Barbara counties since erupting Aug. 1.
Adding to wildfire concerns, lightning accompanying thunderstorms could spark new blazes, especially in mountain areas. Sam Zuber, a meteorologist with the weather service's San Diego office, said monsoonal moisture and the unstable environment created by extreme heat create perfect conditions for thunderstorms.
"Lightning can strike in dry areas up to 15 miles away from where downpours occur," Zuber said Wednesday.
Officials opened cooling centers this week in Los Angeles, where residents are warned to avoid strenuous outdoor activities. The LA County Library activated cooling centers at 21 locations with extended hours from Aug. 21-23.
"LA County Library is committed to supporting the health and well-being of our neighbors," said Skye Patrick, county librarian and director. "We urge everyone to take advantage of these cooling centers and to take necessary precautions to stay safe during this excessive heat warning."
The American Heart Association issued a reminder about the serious cardiovascular health threats posed by extreme heat, particularly for older adults and people with existing heart conditions. When exposed to high temperatures, the body works overtime to stay cool, putting extra stress on the cardiovascular system.
According to the Centers for Disease Control and Prevention, more than 1,200 people in the U.S. die each year directly from extreme heat, and that number is rising along with heat-related cardiovascular deaths. A recent study published in the journal Circulation predicts these deaths could more than double in the next two decades if current climate trends continue.
People with heart disease are particularly vulnerable because their hearts may already be compromised, and dehydration thickens blood and makes it harder for the heart to pump effectively. Certain heart medications, including beta blockers and diuretics, can also increase heat sensitivity.
Health officials urged residents to time outdoor activities for early morning hours, wear lightweight and light-colored clothing, stay hydrated and take frequent breaks in shade or air conditioning.
Candice Catlett, who uses a wheelchair, sought shade as temperatures started spiking Tuesday in downtown Los Angeles.
"It's sizzling hot out here," Catlett said. "I have sunblock. Hopefully, I can find some cold water. I'm trying to stay out of the direct sun."
Forecasters warned that heavy rain from thunderstorms could also cause localized flooding and mudslides.
The Associated Press contributed to this report