(CNN) The deadly heat in the Southwest has claimed another victim.

Authorities in Pima County, Arizona, confirmed that a missing hiker -- 33-year-old Marcus Turowski -- was found dead Tuesday.

Turowski becomes the fourth hiker in the Tuscon area who died due to extreme heat.

One of the other people he was hiking with was found dead Sunday -- 57-year-old Stefan Guenster.

Adrienna Rasmussen, 18, also died Sunday in a heat-related incident.

Further north in Phoenix, a 28-year-old woman died Sunday and a 25-year-old man died Saturday -- both while hiking, according to Larry Subervi, a Phoenix Fire Department spokesman.

And a woman in her 50s died of heat exposure while going for a walk in the middle of the city, Pima County Sheriff Chris Nanos said at a news conference Monday.

Do you know how to recognize the symptoms of heat exhaustion and heat stroke? #BeatTheHeat #CAHeat pic.twitter.com/zHcTW38bU3 — NWS Hanford (@NWSHanford) June 18, 2016

Nanos urged people to stay indoors for their safety -- and for the safety of others.

"If not for your own safety, [then stay inside] for the safety of my team and these volunteers who come out here and do this all the time," he said. "This week, until these temps come down, get your exercise at home. Get your exercise indoors. Or just stay inside. It's too hot."

The heat is on the march

Fortunately for the Southwest, it looks like the heat is heading east into the Rockies and as far away as Illinois.

Heat warnings have been issued for parts of Utah and red flag warnings -- indicating conditions are ripe for wildfires -- are in effect from Montana south into Colorado, CNN meteorologist Dave Hennen said.

As the heat grows out West, so does the threat for severe weather, from the nation's mid-section out to the East Coast.

A map from the National Weather Service shows the parts of the United States that are currently under heat advisories (pink areas face excessive heat warnings, lighter pink shows Red Flag warnings and areas in orange face heat advisories).

About 22 million people, in an area that stretches from the northern Plains to the Mid-Atlantic, face a higher risk of severe weather Wednesday, Hennen said, a threat that will only increase Wednesday in places like Chicago and Milwaukee, where there will be a high risk of tornadoes possible.

Much of the current heat wave can be attributed to a so-called heat dome -- a pattern that can lead to record-setting temperatures and heat waves -- according to CNN Meteorologist Rachel Aissen. A heat dome occurs when air is capped by the upper atmosphere in the same location: The air hits the cap and returns to the surface, continuing to heat it like a convection oven.

If you're in the heat dome, you're in for a hot Mon -- #heatwave in the SW U.S.: https://t.co/mamYizkT9l #weatherhttps://t.co/5SIZea8lFa — Josh Berlinger (@j_berlingerCNN) June 20, 2016

Swarm of wildfires

Fires have been a significant problem in the Southwest.

More than a dozen wildfires have popped up throughout the region as of late Monday.

The largest of them, the Cedar Fire in Arizona, grew by about 10,000 acres in a single day. So far it's scorched more than 40,000 acres and is only 22% contained

Arizona Gov. Doug Ducey declared a state of emergency in Navajo County in order to free up state money to help responders and firefighters.

"In light of the size and scope of the fire, coupled with additional risks posed by dry weather conditions, I have declared a State of Emergency to direct additional state resources and assets to support local response and recovery efforts," Ducey said. "Ensuring the safety of these communities -- and all of the women and men working around the clock to fight this fire -- remains our top priority."

A pair of wildfires also popped up in the San Gabriel Canyon near Los Angeles on Monday.

The two fires, which are together being called the San Gabriel Complex Fire, have burned about 4,900 acres, according to the LA County Fire Department.

Elsewhere in California, evacuations were ordered in San Diego County as fires continue to rage near the U.S.-Mexico border. And a large wildfire in Santa Barbara County also forced mandatory evacuations.