What is a heat dome? Maps show how it's baking California and beyond

The heat is on for western states 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.

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. 

More: First heat wave to scorch the West because of a 'heat dome.' Who will see extreme temps?

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

SOURCE National Weather Service, Climate Prediction Center, NOAA, AccuWeather and Paste BN research