California’s independent system operator – which runs 80% of the state’s grid – has extended what is called a flexible alert, urging residents to reduce their electricity use between 4 p.m. and 9 p.m. until until at least Thursday.
The operator also suggested residents pre-cool their homes to 72 degrees Fahrenheit by 4 p.m., then set their thermostats to 78 degrees or higher during conservation hours. Residents should also avoid charging electric vehicles or using large appliances, he said.
The load on the grid increases during the late afternoon hours as the use of air conditioners increases while the supply provided by solar energy decreases, according to the electricity grid operator.
More than 40 million people are subject to excessive heat alerts in seven western states through Labor Day weekend, including densely populated cities such as San Francisco and Los Angeles.
“This will be the longest and most intense heat streak so far this calendar year,” Alexis Clouser of the National Weather Service in San Francisco told CNN.
The California grid will be limited in its ability to import power as neighboring states anticipate high temperatures, the operator said.
“We are monitoring any potential energy supply shortages and any changes in conditions, such as wildfires or generation or transmission outages, that would impact supply or the grid,” he said. in an email.
Governor Gavin Newsom has declared a state of emergency for California.
“We expect this extreme heat to be of a duration the likes of which we haven’t seen in some time,” he told a news conference.
Labor Day is expected to be the hottest day of this lingering heat wave, with other days expected to see temperatures soar 15 to 20 degrees Fahrenheit above normal.
“Large-scale daily high temperature records are possible, with some locations potentially hitting monthly records,” the Weather Prediction Center said.
“It’s deadly heat”
Other affected states include most of Nevada, parts of Arizona, Idaho, Utah, Oregon and Washington state, according to CNN Robert Shackelford.
Temperatures could reach 116 degrees in areas with excessive heat warnings and up to 105 degrees in heat advisories, he noted.
Heat advisories are in place for Boise, Idaho; Reno, Nevada; and Seattle.
Cities including Los Angeles, San Diego, Palm Springs, Fresno, San Francisco, Sacramento and Redding in California are under excessive heat warnings – although not all are expected to see temperatures up to 116, Shackelford said.
In California, the state of emergency will allow power plants to produce additional energy and give the green light to the use of emergency generators to reduce energy used during peak hours, according to the governor’s office . It also allows ships to reduce their consumption of grid energy.
Newsom noted that extreme drought conditions limit hydroelectric power sources as water reservoirs run out, which he acknowledged adds to the lack of “power reliability”.
“On the supply side, we’re challenged by these extremes, and on the demand side, unsurprisingly, people are ramping up the air conditioning,” Newsom explained. “People naturally try to escape the heat, so we have to take on that double challenge again.”
In the meantime, forecasters are warning people to take extreme heat seriously as it can be life threatening.
“It’s killer heat, so use common sense,” said Joe Sirard of the National Weather Service in Los Angeles. “Some people don’t pay enough attention to the forecast and can put themselves in danger and die because of it. Obviously it’s a very sad thing to say, but people need to be aware that the heat can be deadly.”
In fact, heat-related deaths have exceeded hurricane-related deaths by more than 15 to 1 over the past decade, according to data tracked by the National Weather Service.
CNN’s Taylor Romine, Cheri Mossburg, Jennifer Gray, Brandon Miller, Judson Jones, Monica Garrett and Taylor Ward contributed to this report.