Tens of millions of Americans will face sweltering temperatures this weekend as “dangerous heat” expands westward, according to the National Weather Service.
On Saturday morning, about 50 million people were under some form of heat alert, either an excessive heat warning or heat advisory. Most of the advisories were issued in the southern part of the country, including Arizona, Texas and Alabama.
And while the Southeast will see a brief respite from the intense heat this weekend, according to AccuWeather, some of the most extreme heat will ooze into the south-central and southwestern U.S. over the next few days.
How hot will it get?
In Phoenix, temperatures will rise above 110 degrees as early as the weekend and stay there through much of next week. By Monday, Phoenix should see a high temperature of 114 degrees, the Weather Service said, which is extreme even by that city’s notoriously hot July standards.
In Dallas, the Weather Service asked and answered: “When will this heat go away? The short answer is … not any time soon. In fact, it is going to get worse this weekend before it gets better.” Highs of over 100 degrees are forecast for the next several days, along with punishing humidity.
In Salt Lake City and Denver, the Weather Service warned of near record heat over the weekend as temperatures were forecast to approach 100 degrees.
In addition, many locations will have record-high overnight temperatures that will prevent some areas from cooling off.
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What’s causing the heat wave?
Blame it on a “heat dome,” which occurs when a persistent region of high pressure traps heat over an area, according to William Gallus, professor of atmospheric science at Iowa State University.
“The heat dome can stretch over several states and linger for days to weeks, leaving the people, crops and animals below to suffer through stagnant, hot air that can feel like an oven,” Gallus said in an article in the independent news organization The Conversation.
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As the heat dome shifts to the west this weekend and into next week, temperatures will be on the rise, AccuWeather said. Underneath a heat dome, sinking air causes temperatures to climb, and precipitation and cloud cover tend to be limited.
“A resilient heat dome that has brought hot weather to the southern Plains this week will spread into the Southwest and park itself there, likely through much of next week,” said AccuWeather meteorologist La Troy Thornton.