The rising temperatures baking much of the desert Southwest this week are not only strikingly high but also unusually persistent.
In forecast for the Phoenix area, where the temperature on Monday was expected to reach 106 degrees, the National Weather Service said the duration of the heat wave will be “one of the longest, if not the longest, depending on how it is measured.”
Sweltering temperatures are likely to continue for at least a week in the area, possibly approaching record levels by the weekend, according to Tom Frieders, a meteorologist with the Weather Service in Phoenix.
Nighttime temperatures there this week will barely dip below 90 degrees, and even the cooling thunderstorms that usually accompany monsoon season, which begins around this time of year, have been delayed.
“This year, we’re seeing a bit of a lag in the development towards the monsoon thunderstorm season,” Mr Frieders said. “And so with that, we ended up seeing temperatures a little warmer during the day.”
The heat wave now set over the desert Southwest – caused by a “heat dome” of high pressure – has also brought sweltering temperatures to parts of Texas and New Mexico. Experts estimate that more than 50 million people across the United States live in areas expected to have dangerous levels of heat.
“It looks like it’s going to be pretty oppressive out here,” said Capt. Darren Noak of Austin-Travis County Emergency Medical Services, who conducted a helicopter rescue Sunday to treat a person overcome by the heat in Popular. hiking spot west of Austin, Texas.
As Capt. Noak spoke Monday afternoon, the heat index in the city — a measure of how the air feels that takes into account both temperature and humidity — had climbed to an expected high of 109 degrees.
Capt. Noak said Austin residents enjoyed some relief last week when high temperatures dropped below 100 degrees for several days and EMS fielded just 39 heat calls, compared to 74 the previous week.
But now, “the weather forecasts are for above 100-degree temperatures for at least the next two weeks straight,” he said. “I would imagine it’s going to shoot up there again this week.”
Orlando Bermudez, a forecaster with the Weather Service in Austin, said residents of central Texas could “copy and paste” the same basic forecast for the next two weeks: hot and dry.
“The story from the week into the weekend into next week is heat,” he said, predicting an almost unbroken pattern of triple-digit temperatures most likely extending at least through July 20.
Julie Engel, the president of the Greater Yuma Economic Development Corporation in southwest Arizona, said residents in the area have been dealing with such temperatures for a long time.
“It’s really not something out of the ordinary for us,” she said. Builders and farm workers know how to adapt, she added, for example by starting their work days hours before dawn.
Still, temperatures across the region are dangerous for many people, according to Zack Guido, assistant research professor at the Arizona Institute for Resilience in Tucson.
“Most of the challenges associated with these extreme climate conditions fall on people with fewer resources,” Dr. Guido said, adding that high nighttime temperatures only added to the risk.
“If you don’t have air conditioning at night, and the temperatures stay above 90 degrees Fahrenheit, that has been attributed to physiological stress that can be quite harmful,” he said.
John Washington contributed reporting.