The scorching weather that ravaged the Southwestern United States last week, with highs consistently in the triple digits, will cool somewhat this week, but life will remain more than uncomfortable for 23 million people still under an excessive heat advisory.

Although weather forecasts show Sunday topping out at 116 degrees in Phoenix — with some parts of the desert climbing as high as 120 degrees — meteorologists say the Southwest will begin to cool off in the coming days.

Phoenix is experiencing weather that is 10 to 15 degrees hotter than average, according to Jon Rowe, a meteorologist for The Weather Channel.

But by next week, temperatures should hover just above the average high of 106 degrees.

People cool off Friday at Dockweiler State Beach in Playa del Rey, California. Frederic J. Brown / AFP - Getty Images

"It's not unusual for [the area] to be really hot. It's the desert," Rowe said.

Heat warnings remain in effect for until 8 p.m. MT Monday in central Arizona, southern Nevada and parts of southeast California, the National Weather Service said in an alert.

Warnings for the three states advise that the weather could get so bad that heat-related deaths could occur. People most at risk are those working or exercising outdoors during the daytime, the elderly and those without access to adequate air conditioning, according to the alert.

A Maricopa County sheriff's deputy said he hadn't heard of any heat-related deaths in this most recent heat wave, but the number for heat-related deaths passed 100 last year.

Related: Texas Mother Accused of Leaving 2 Children to Die in Hot Car to Teach a 'Lesson'

Up the West Coast, temperatures verged on record-breaking in Washington state, where the high in Seattle was expected to reach 95 degrees. The previous record was 88 degrees, was set in 2006.

That same year, Portland, Oregon, hit a record of 101 degrees, which could be tied by Sunday's sweltering heat.

Until temperatures cool, the National Weather Service advises to avoid alcohol, sugar and caffeine and to drink more water than usual.

It also recommends taking frequent refuge in public areas with air conditioning, like libraries, community centers, government buildings, malls and specially designated stations.