By Aya Elamroussi, CNN
The savage heat that has gripped several states in the West will persist through the holiday weekend — and for the third day in a row, Californians are being advised to curb their electric consumption to avoid power outages.
More than 45 million people were under heat alerts across most of California, Nevada, Washington, Oregon and Idaho, and some parts of Utah and Arizona.
Forecasts call for temperatures above 100 on Friday in cities such as Redding, 105; Fresno, 109; and Bakersfield, 106, in California; Redmond, Oregon, 103; and Yakima, Washington, 100.
In Nevada, Las Vegas could hit 110 degrees.
“September is kicking off with scorching temperatures throughout the western US, as highs are once again anticipated to threaten daily and even monthly records headed into Labor Day Weekend,” the Weather Prediction Center said Friday morning.
“The heat wave will pose a high to very high risk to the general population, particularly the elderly and those without adequate air conditioning, due to both the intensity of the high temperatures and duration of the heat wave,” the National Weather Service warned earlier.
High-temp records for September were set on Thursday in Salt Lake City, with a temperature of 102, and in Lancaster, California, 112. Dozens of daily records were reached across the region.
Millions of Californians are urged to reduce electricity use between 4 p.m. and 9 p.m. Friday.
The California Independent System Operator — which manages 80% of the state’s power grid — issued the third Flex Alert of the week, asking residents to be mindful of their electricity use.
“The Flex Alert covers that time of day when the grid is most stressed from higher demand and less solar energy,” the operator explained.
The operator also asked residents to pre-cool their homes before 4 p.m. and then set their thermostats to 78 during reduction hours and to avoid charging their electric vehicles.
Los Angeles, Santa Barbara, Orange and Fresno counties have opened cooling centers. Officials have also compiled a list of all the cooling centers in the state.
Why this heat wave is different
High summer temperatures have been the norm in California, but what makes this heatwave especially dangerous is the length of time it’s expected to linger over much of the state. In addition, there will be little relief during overnight hours.
“Even after the sun goes down, heat can be a real danger — especially in large cities. Dark pavement and buildings are very effective at absorbing heat,” the weather service office in Los Angeles said.
And that’s why higher temperatures are more common in large cities, making them susceptible to becoming an “urban heat island,” the service explained.
The weather service defines a heat wave as a period of abnormally hot and humid weather lasting for more than two days.
Excessive heat has killed more people than any other extreme weather event in the US. Heat deaths have outpaced hurricane deaths by more than 15-to-1 over the past decade, according to data tracked by the National Weather Service.
Climate change imposes conditions that have been making extreme weather events more deadly and more common.
In Arizona, where temperatures are expected to hit triple digits this weekend, 111 people have died from heat-related complications this year in Maricopa County as of Wednesday, according to a report from the county’s public health department.
The report indicates 38% of the deaths have been in people 50 to 64 years old, and 80% of the deaths occurred outdoors.
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CNN’s Paradise Afshar, Taylor Romine and Alaa Elassar contributed to this report.