Heat dome set to bring more sizzling temperatures to the Southwest a day after Death Valley hit 122 degrees

Driving this prolonged, unseasonable heat is a robust heat dome – a large area of high pressure that parks over an area, traps air and heats it with abundant sunshine for days or weeks.

More than a dozen daily high temperature records fell earlier this week in the West as the heat dome strengthened. A few dozen more could be broken through the weekend.

“More records may be tied or broken as excessive heat across the California’s Central Valley and much of the Desert Southwest continues,” the National Weather Service said.

Heat advisories are in effect for more than 25 million people in California, Nevada, Arizona, Utah and New Mexico. A majority of these heat alerts remain active through Friday. Alerts in Las Vegas and Death Valley will last into Saturday.

The searing heat has already taken its toll. Since last weekend, multiple people in different parts of the US have died due to heat-related illnesses.

A handful of cities could see the day’s high temperature record fall on one or more days this week. Several temperature records were broken Thursday across states including California, Arizona and Nevada.

The Las Vegas area saw several record-breaking temperatures, with Las Vegas reaching 111 degrees Thursday, topping the record of 110 degrees set in 2010.

In California, a high of 122 degrees in Death Valley broke a record set in 1996. And in Fresno, a 121-year-old record was tied Thursday, with the daily maximum high temperature reaching 107 degrees. Temperatures also reached 106 degrees in the Sacramento area.

For Phoenix, a record high of 113 degrees was set Thursday. In Flagstaff, temperatures could reach between 105 to 111 degrees through Friday night.

The National Weather Service in Salt Lake City, Utah, says early-season heat will result in high temperatures up to 20 degrees above normal through at least Saturday.

Several people across US have died from heat-related illnesses

Excessive heat is the leading weather related killer in the US, according to the National Weather Service.

“This is especially true in the urban centers, where population density, the urban heat island, and building construction exacerbate the effects of excessive heat,” the weather service says. “A combination of high heat and humidity can lead to heat related illness, including heat cramps, heat exhaustion, and heat stroke.”

Four migrants died “from heat stroke and dehydration” while triple digit temperatures baked the US-Mexico border last weekend, according to the US Border Patrol, El Paso Sector.

In the East, a 59-year-old man died of heat-related complications in Prince George’s County, Maryland, officials said Wednesday. Additional details about the man’s death, which was the state’s first heat-related death of the year, were not released.

Heat also proved challenging for firefighters battling a blaze in California’s Napa County Wednesday. Four firefighters were sent to area hospitals for injuries related to difficult terrain and “hot summer conditions,” according to CAL Fire’s Sonoma-Lake-Napa Unit. All four are expected to make full recoveries.

Phoenix emergency responders on Thursday say they hospitalized 11 people due to heat exhaustion while they were attending a Donald Trump rally at the Dream City Church.

With the risk of heat-related illnesses increasing for millions across the country, officials in several states are trying to keep residents safe during the smoldering heat. In California, cooling centers have been set up for those affected by triple-digit heat. As Texas contends with both severe storms and excessive heat, a state disaster declaration remains active.

Hazardous heat expected to continue into the weekend

Several daily records could be tied or broken on Friday as the heat persists. Las Vegas is forecast to hit 109 degrees, which would tie the daily record for June 7 set in 2013. Albuquerque could reach 100 degrees, which would tie the record set in 1981.

Heat will continue through the weekend before easing off a bit early next week. However, many typically hot areas in the West will still have to contend with temperatures up to 10 degrees above normal.

Through Saturday, the Las Vegas metro area is at “extreme” risk from the heat. The highest level on the heat risk scale means residents without enough cooling and hydration will be impacted, and “impacts are likely in most health systems, heat-sensitive industries and infrastructure.”

Meanwhile, several more large metro areas in Arizona, California, New Mexico and Texas will face a “major” level 3 of 4 heat risk.

California can see high temperatures up to 108 degrees, parts of Nevada and Arizona could potentially see high temperatures between 105 to 114 and Death Valley’s high temperature could again exceed 120 degrees. Warm nighttime lows in the region will make it difficult for those vulnerable to extreme conditions to be able to cool off.

Heat will remain hazardous for parts of the Southern High Plains and South Texas into Saturday, according to the National Weather Service.

Summerlike heat will expand northward Friday and reach the Northwest. Records could be broken in parts of Oregon, Washington and Idaho from Friday through the weekend.

While it won’t be record-breaking, Seattle will contend with high temperatures in the upper 70s Friday and could come close to 80 degrees on Saturday. Highs like these are 10 degrees warmer than what’s typical for early June.

CNN’s Mary Gilbert and Joe Sutton contributed to this report.