An extended record-setting heat wave is scorching the West and many Californians are being asked to turn up their thermostats

By Nouran Salahieh, CNN

As a prolonged record-setting heat wave tightens its grip on the West, millions in California are for a fifth day being asked to reduce their energy consumption amid worries about a strained power grid.

More than 45 million people throughout the Western US are currently under excessive heat warnings and advisories. Many are spending the holiday weekend sweltering in triple-digit temperatures, including in California, Oregon and Idaho, according to the National Weather Service.

Multiple cities have already seen recording-breaking hot temperatures. Boise, Idaho, sizzled under a record temperature of 101 degrees Friday, tying its previous daily record set in 1950. Salt Lake City hit 103 degrees Saturday, beating its previous record of 98 set in 2017. In Southern California, Burbank set a new monthly record for August at 112 degrees on Wednesday.

The dangerous heat wave is expected to continue to impact much of the West through the weekend and into the middle of the week. Temperatures will range 15 to 20 degrees above normal with highs over 100 degrees.

Temperatures as high as 110 degrees with nighttime lows in the 80s are possible Sunday.

In California, where some areas are seeing blistering temperatures 10 to 25 degrees above normal for this time of year, the heat is already increasing demand for power and straining the power grid.

And the hottest temperatures are yet to come, Sarah Rogowski with the National Weather Service said in a Saturday briefing.

The California Independent System Operator — which manages 80% of the state’s power grid — extended another Flex Alert into Sunday, asking residents to conserve electricity to protect the power grid due to the potential for a supply shortfalls.

Despite the heat, Californians are being urged to set thermostats to 78 degrees or higher, avoid using major appliances, and turn off all unnecessary lights between the hours of 4 p.m. and 9 p.m. Sunday. The operator asked residents to pre-cool their homes before 4 p.m.

“Additional Flex Alerts will likely be called as heat will only intensify through Tuesday, with little relief from triple-digit temperatures seen over the next several days,” California Independent System Operator said in a news release.

During the past three days, the power operator received the highest demand for power it has seen since September 2017, Elliot Mainzer, president and chief executive officer of the California Independent System Operator, said during the news briefing Saturday.

“Those last few days are likely to be a dress rehearsal for what’s going to be a much more significantly stressed set of conditions here,” said Mainzer.

He stressed that residents’ compliance with the alert is critical to ensuring there are no blackouts. “That response can be the difference between the light staying on or not,” Mainzer said.

Power provider NV Energy, which serves more than 1.5 million homes and businesses throughout Nevada, has also been asking residents to cut back on their electricity use to avoid straining the power grid between the hours of 5 p.m. to 8 p.m.

Wildfires grow as California bakes

Scorching temperatures across the region, coupled with low relative humidity, also means increased wildfire risk. Parts of Northern California, southeast Oregon, northwestern Nevada and southwestern Idaho are under critical fire weather, according to NOAA.

The National Weather Service in Spokane, Washington, said regional and local wildfires are degrading air quality.

Two Northern California wildfires that broke out Friday quickly grew, both forcing evacuations.

“Over the last several days, we’ve definitely seen a steady increase in the number and the size of wildfires burning throughout California,” Chief Deputy Director of Cal Fire Chris Anthony said during the Saturday news conference.

The Mill Fire in Siskiyou County burned an estimated 4,254 acres as of Saturday evening and had destroyed 50 structures.

In the same county, the Mountain Fire grew to cover 4,812 acres.

Farther south, the Route Fire in Los Angeles County was at 5,208 acres Saturday evening with 87% containment, according to an update from the Los Angeles County Fire Department. The blaze destroyed two structures and threatened hundreds more.

Relief from the heat expected Thursday

The heat dome producing the heat wave will slowly spread eastward into the central and northern plains by mid-week. More than 150 high-temperature records could be set or tied through Thursday, according to CNN Meteorologist Derek Van Dam.

While the sweltering hot temperatures are expected to continue through the middle of the week, with little relief during overnight hours, cooler temperatures are expected Thursday.

“There is some relief in sight with … cooler temperatures reaching northern parts of the state by Thursday, moving further south through Thursday and Friday,” Sarah Rogowski with the National Weather Service said Saturday in a briefing.

“However, temperatures are remaining above normal, and that’s expected to continue through the middle parts of the month,” she added.

Extreme weather events, including heat waves like the current one, have been occurring more often and will continue to be more frequent and intense due to the impacts of human-driven climate change, scientists have warned.

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CNN’s Paradise Afshar, Derek Van Dam and Aya Elamroussi contributed to this report.