US Southwest faces historic heat wave, putting millions at risk

Millions of people across the Southwest are living through a historic heat wave, with even the heat-experienced desert city of Phoenix being tested since temperatures have hit 43 degrees Celsius for 13 consecutive days.

More than 111 million people across the United States were under extreme heat advisories, watches and warnings, The National Weather Service reported Wednesday. Huge swaths of Oklahoma, Texas, New Mexico, Arizona and California were experiencing temperatures above 32°C.

“It is imperative users take action to limit their exposure to the oppressive hot weather as it looks to stick around for the time being,” the National Weather Service said in a separate bulletin.

Forecasters in Phoenix said the long-duration heat wave is extremely dangerous for people's health and could persist into next week as a high pressure dome moves westerly from Texas into central California.

“It's important for the temperatures to go down at night to offer relief to people needing to recover from the daytime heat,” said Sean Benedict, lead meteorologist with the National Weather Service in Phoenix.

David Hondula, chief heat officer for the city of Phoenix, noted Wednesday that “any long period without a break from the heat is dangerous.” He said the duration of the heat wave was “notable.”

Highest temperatures in recorded history

With no end in sight, this week El Paso, Texas, endured its 27th consecutive day of 38°C temperatures on Wednesday. The previous record for consecutive triple-digit highs was 23 days in 1994, when an all-time high of 45.5°C was recorded.

“It’s unprecedented," said Zak Aronson, a national weather service meteorologist in Santa Teresa, New Mexico. “It’s never happened here before in recorded history.”

He said temperature records for the area date back to 1887.

Since 1983, both the average and daily summer high temperature in Texas have gone up 1.6°C, according to the National Oceanic and Atmospheric Administration, which oversees the weather service.

The summertime high temperature for Las Vegas has increased 2.4°C in the same period while its average daily temperature has increased 2.2°C.

How Phoenix handles the extreme weather could become a model for other cities, especially those that are less accustomed to high temperatures but are now roiled by heat waves fueled by drought and climate crisis.

Two years ago, the city of Phoenix opened a small office with an annual budget of about $1 million to oversee heat response and mitigation. Since then, it has planted more shade trees; designed cool, white roadways to deflect heat; and expanded shelters for homeless people who have accounted for half of Phoenix metro's heat-associated deaths.

There were 425 confirmed heat-associated deaths in Maricopa County last year, with more than half of them occurring in July. Eighty percent of the deaths occurred outside.

Fueling the current heat wave is the delayed arrival of this year's monsoon rains. The season officially begins on June 15 and can bring powerful storms with bursts of precipitation.

Despite the extreme heat, Arizona’s largest county of 4.5 million people had the biggest gain in overall population of any U.S. county last year, with a jump to almost 57,000 new residents, mostly from people moving from other states.