California and Arizona brace for 'historic' heat wave with possible temperatures over 120°F

A Los Angeles Fire Department helicopter drops water on a brush fire next to a freeway.
A Los Angeles Fire Department helicopter drops water on a brush fire in the Elysian Park area on July 7 in Los Angeles. (Mark J. Terrill/AP) (ASSOCIATED PRESS)

The formation of yet another "heat dome" over the southwestern United States is expected to cause temperatures in parts of California and Arizona to rise above 120 degrees Fahrenheit in the coming days.

One of the hottest places on the planet, California's Death Valley, is expected to see temperatures as high as 125°F to 130°F this weekend. Portions of the Central Valley further north are also expected to see temperatures as high as 117°F.

The National Weather Service also issued an excessive heat warning for Phoenix through Sunday, with temperatures forecast to reach 118°F on Saturday, still a few degrees below the all-time record of 122°F.

"Widespread areas of Major Heat Risk will increase to Extreme levels this weekend," the NWS forecast office in Phoenix said in a statement.

Temperatures in the city have already topped 110°F for the last 12 consecutive days, nearing its all-time record of 18 consecutive days over 110°F, which was set in 1974. In the early morning hours Wednesday, Phoenix did break a notable record, when the all-time low temperature registered on July 12 only fell to 94°F.

Temperature records are also expected to fall in Reno, Nev., and Las Vegas is forecast to reach a blistering 117°F this weekend, which would tie the city's all-time record.

More evidence of climate change

A runner jogs along a lake at sunrise.
A runner jogs along Tempe Town Lake at sunrise on Wednesday in Tempe, Ariz. (Matt York/AP) (ASSOCIATED PRESS)

Caused by a surge of high pressure that traps ocean heat over land, the latest heat dome comes as the National Weather Service has issued heat alerts for 108 million Americans and the Earth recorded its warmest week and its hottest June in recorded history. Pulling back the lens, with the June figures, the planet recorded its 532nd consecutive month of above-average temperatures. An ocean heat wave now spans the globe, sending water temperatures in the Florida Keys to an unprecedented 97°F, and Canadian wildfires, made worse by record-breaking temperatures, continue to burn out of control.

While skeptics counter that summers are always hot, the fact is they are getting hotter and countless studies have shown that those higher temperatures are having a wide array of disruptive consequences, such as the historic flash flooding in New York and Vermont this week and record low Antarctic sea ice.

"Climate change is not necessarily bringing about completely brand-new types of weather," UCLA climate scientist Daniel Swain told reporters Monday. "It is shifting the envelope of weather that we experience. It's not that we've never experienced heat waves before, or extreme precipitation events, or floods or wildfires. But what it's doing is changing the character of those events. It's upping the ante."

Health risks

A Salvation Army volunteer hands a bottle of water to a man at a heat relief station as one of her colleagues looks on.
Salvation Army volunteer Francisca Corral, center, gives water to a man at a heat relief station on Tuesday in Phoenix. (Matt York/AP) (ASSOCIATED PRESS)

As the current heat wave in the Southwest inches its way east, officials are warning the public to take health precautions against the potentially deadly temperatures.

"The best advice is to drink plenty of fluids, stay out of the sun, and in an air-conditioned place," the National Weather Service says on its website. "If you work or spend time outside, take extra precautions, such as frequent rest breaks in shaded or air conditioned locations. Also wear clothing that is light weight and loose fitting."

A study released this week concluded that the 2022 heat wave in Europe, which occurred during the continent's hottest summer on record, killed 61,000 people.

According to the U.S. Department of Agriculture, more than 250 Americans and over 400 Canadians died in the 2021 heat dome in the Pacific Northwest that shattered all-time temperature records.