The heat is on for the California desert and much of the western United States, which are gripped in the nation’s first heat dome of the year.

And it’s a scorcher, with temperatures reaching into the triple digits for major cities such as Las Vegas, Phoenix, Redding, California, and Cedar City, Utah.

Palm Springs area to see extreme heat

The Coachella Valley, which usually sees triple digits this time of year, is expected to see temps surge past 110 degrees during the second half of this week.

The scorching forecast has led the National Weather Service to issue an excessive heat watch for the Coachella Valley, with the hottest temperatures expected to occur Wednesday, Thursday and Friday. Such watches are issued when there is potential for potentially dangerous heat.

The watch warns that the latter half of the week will be the first time this year when the Coachella Valley sees temperatures of 108 to 113 degrees, with Friday expected to be the hottest day. The temperatures are expected to be fairly consistent throughout the valley and nearby desert areas, with slightly hotter temperatures expected on the western side of the valley.

The heat wave that has been killing hundreds of people in Mexico over the past several weeks is partially to blame for the coming heat. Mexico’s intense heat is caused by a powerful heat dome of high pressure that is gradually moving northward. The cauldron of misery has parked itself over portions of the Southwest, sending temperatures skyrocketing.

Where is the heat dome located?

Though the entire West is likely to be sweltering, forecasters at the Climate Prediction Center have determined that June 8 to June 18 will be especially hot across the states of Arizona, Colorado, Idaho, Montana, Wyoming, Nevada, New Mexico, Oregon, Utah and and inland California.

Unable to view our graphics? Click here to see them. 

What is a heat dome?

A heat dome occurs when a persistent region of high pressure traps heat over an area, according to William Gallus, professor of atmospheric science at Iowa State University.

“The heat dome can stretch over several states and linger for days to weeks, leaving the people, crops and animals below to suffer through stagnant, hot air that can feel like an oven,” Gallus said in an article in The Conversation.

.

Persistent heat wave conditions

Forecasters say that as the jet stream nudges its way north in the coming days, the heat will build into the Great Basin. Phoenix’s high is expected to reach 112 degrees on Thursday and 113 degrees on Friday, according to AccuWeather.

Experts caution that there is little chance of residents cooling off when the sun sets because the heat will continue overnight.

Heat index chart calculates danger of humidity, heat

The National Weather Service warns that “extreme heat and humidity will significantly increase the potential for heat-related illnesses, particularly for those working or participating in outdoor activities.”

This chart shows how hot it feels when humidity and high temperatures are combined:

Residents are being advised by National Weather Service meteorologists to stay hydrated and avoid direct sunlight.

CONTRIBUTING: Doyle Rice of USA Today and Paul Albani-Burgio of The Desert Sun

SOURCE: National Weather Service, Climate Prediction Center, NOAA, AccuWeather and USA TODAY research

This article originally appeared on USA TODAY: As heat dome bears down on California, maps show how it works