The Southwest is in for peak dog days as a looming heat wave has triggered extreme heat warnings and advisories for 80 million people from the U.S.-Mexico border to southwest Utah.

Federal forecasters said a swirling system of warm, descending air over the crosshairs that divides Arizona, Utah, Colorado and New Mexico will toast the region through the weekend.

“An anomalously strong ridge of high pressure centered over the Four Corners states will lead to a significant heat wave,” the National Weather Service said in a national forecast discussion Tuesday.

Extreme heat warnings, which predict certain danger, begin Wednesday morning in Southern California for parts of Los Angeles, San Diego and Orange counties, as well as Palm Springs. The warnings also begin Wednesday for Las Vegas, Phoenix and Tucson, Arizona. They are scheduled to remain in effect through the weekend.

Los Angeles Mayor Karen Bass said the city was expecting “potentially some of the hottest temperatures of the summer.” Cooling centers are opening in the city, while Gov. Gavin Newsom is moving firefighting resources to the region.

In agricultural El Centro, California, where temperatures remained in the triple digits after nightfall, a child left unattended in a hot vehicle Monday later died at a hospital, police said.

Temperatures in the 90s are expected as far north as the Seattle region Saturday, according to the service, and Portland, Oregon, has a fire weather watch in effect for Thursday.

On Friday, Phoenix is expected to reach a high temperature of 112 degrees, Las Vegas is expected to reach 110, and Death Valley National Park’s Furnace Creek Visitor’s Center is forecast to report 120 degrees, according to the weather service.

Maricopa County, Arizona, officials on Tuesday reported 44 deaths last week for which heat was a cause or contributor.