Dangerous Heat Wave Scorches Southwestern U.S.

Chris Mitchell sprays water on his face to cool off while wearing a Darth Vader costume along the Las Vegas Strip on June 20, 2017.

The first day of summer brought some of the worst heat the southwestern U.S. region has seen in years. Arizona, Nevada and California saw dramatic temperatures on Tuesday and researchers say heat waves like this one are going to grow more frequent.

A construction crew sits under an excavator to avoid the heat during while taking a break on June 20 in Tempe, Arizona. Phoenix recorded a high of 119 degrees on Tuesday with an excessive heat warning in place until Saturday.

Helicopter crews put out hot spots in Utah on June 18. Firefighters in Utah were battling a wildfire on Monday that shut down a highway and forced hundreds of people to flee a ski town.

Martin Norman prepares for a day on the fire line with fellow firefighters on June 19 in Parawan, Utah.

Women cool off their dogs at a park on June 20 in Las Vegas.

Kids cool off at Spring Valley Lake in Victorville, California on June 19. Death Valley, California reached 127 degrees Tuesday and Palm Springs hit 122 degrees, tying the temperature for the same day last year.

A woman uses an umbrella to shield herself from the sun on June 20 in Phoenix. The heat wave comes amid new research findings that nearly 1 in 3 people now experience 20 days a year when the heat reaches deadly levels.

A boy finds some relief from the heat under a cascading waterfall at the Wet-N-Wild Water Park on June 20 in Phoenix.

Crew members take a break to try to stay hydrated and cool as temperatures climbed to near-record highs on June 20 in Phoenix.

A woman shields herself from the sun while walking along the Las Vegas Strip on June 20.

A woman walks through a row of misters on June 19 in Tempe, Arizona. Airlines canceled flights in Phoenix and doctors urged people to be careful around concrete, playground equipment and vehicle interiors on Monday.

A radio station employee plays with a puppy wearing elastic booties at a PetSmart in Tempe, Arizona on June 20. Phoenix radio station KSLX handed out the protective coverings to protect dogs' paws from the hot pavement.

An air conditioning repairman climbs down a ladder to get supplies from his truck in Tempe, Arizona on June 19. Repairmen are constantly on call throughout the summer. 

Lori Mantz sprays water to cool down her horse Chavi on June 19 in Las Vegas.