Heat waves can dry up vegetation and are often followed by stronger winds, which could exacerbate the fire risk after temperatures fall, Ms. Tolmachoff said.
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On Thursday, Gov. Gavin Newsom of California signed an emergency proclamation to “free up additional energy capacity amid extreme temperatures across California.”
The California Independent System Operator, which oversees the state’s electrical grid, issued a statewide alert that called for state residents to conserve energy from 3 to 9 p.m. Alerts were also issued for Sunday and Monday.
“The ISO recognizes that reducing energy use during the hot time of the day is a hardship, especially for those working from home or for families with children schooling at home,” it said in a statement on Saturday. “However, if a large enough number of consumers conserve even in small ways, they can help grid operators avoid more serious system emergencies.”
At the Back on the Beach Café in Santa Monica, Fred Deni, a co-owner, said that there had been a line of customers into the parking lot at 7:45 a.m. and that business had not slowed, despite the heat wave and the coronavirus pandemic.
“When I opened at 8, my 28 tables were filled, and we continue to be filled,” said Mr. Deni, who has been a co-owner of the beachfront restaurant for more than 40 years. “The shoreline looks like it’s July 4 all over again.”
Extreme heat is in the forecast for other Western states, too, including Nevada, Utah and Arizona. In Colorado, temperatures in the Denver area are expected to reach the high 90s on Saturday and Sunday, breaking records for early September.