A potentially record-breaking heat wave is expected to push temperatures into triple digits across the western U.S. this week, prompting warnings from government officials as authorities across the region set up cooling shelters.

Millions of people in southwestern Oregon, California, parts of Arizona and western Nevada are under extreme heat warnings from Tuesday through Friday.

The highest temperatures are expected in Furnace Creek in Death Valley National Park, where temperatures could reach 120 degrees this week. Meanwhile, in the Palm Springs area of ​​Southern California and the Coachella Valley, afternoon temperatures could reach 118 degrees.

Federal meteorologists said major cities including Los Angeles, Phoenix, Las Vegas and Portland could all exceed 100 degrees, according to the weather service. Los Angeles Mayor Karen Bass said emergency personnel have begun preparing for the heat wave and authorities are setting up cooling centers around the city.

“Homeless people, the elderly, children and people with health problems are most at risk for heat illness,” the Los Angeles weather bureau said on X. “Daytime temperatures between 95 and 105 will become common off the coast.”

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Heatwave in the southwest is not uncommon at this time of year

According to Heather Zehr, senior meteorologist with AccuWeather, the approaching period of scorching heat is not unusual for Southern California, western Nevada and southern Arizona this time of year.

“September is actually generally quite a warm month because they are so far southwest and the climate is so dry. The highest normal temperatures are usually reached in late August and early September,” she said.

Zehr noted that the approaching heat wave will be much less severe than an earlier heat wave that broke records in the Southwest in July. The earlier burst of hot weather brought temperatures in Phoenix to 118; midday temperatures in Las Vegas to 120 and peak temperatures in the desert region of Palm Springs to 124 degrees. This week, each of those areas is forecast to remain several degrees below their July midday temperatures.

The same cannot be said of the Northwest.

Zehr said southwestern Oregon typically starts to cool off in early fall as Arctic air moves into the region. However, the heat wave could challenge daily record highs in the Willamette Valley, including cities like Portland and Medford, as meteorologists predict temperatures could reach as high as 105 degrees.

“This is a little more unusual for them,” Zehr said, referring to the heat wave sweeping across Southern Oregon.

How to stay safe during a heat wave?

To avoid heatstroke and sunburn during prolonged heat waves, experts advise staying indoors, drinking plenty of water and, if you must go outside, wearing protective sunscreen or sun-protective clothing.

Seemal Desai, president of the American Academy of Dermatology, previously told USA TODAY that people should especially stay indoors between 10 a.m. and 2 p.m., the hours of peak sunlight. People should drink water, not just caffeinated beverages or sports drinks, which are hydrating but contain other chemicals and additives, Desai said.

Kelly Olino, an associate professor of surgical oncology at Yale School of Medicine, urged people to be alert for the serious warning signs of heat stroke or heat-related illness: nausea, vomiting or dizziness.

The National Weather Service issued warnings Tuesday reminding people to check their cars for children and pets before leaving them unattended. The weather service said temperatures inside cars can reach lethal levels in minutes.

Contributors: Doyle Rice, Cybele Mayes-Osterman, USA TODAY

This article originally appeared on USA TODAY: Heat wave in the West: Temperatures could break records, experts warn