Record-smashing Southwest heat dome to strengthen, expand east through late July
A heat dome that has brought consistent triple-digit temperatures to a large swath of the southwestern United States since June will increase in size and intensity over the next week or so, bringing record-setting heat to millions more, according to AccuWeather forecasters.
In the interim, the Desert Southwest will continue to roast today, with Phoenix adding to its record-setting streak of high temperatures at or above 110 degrees. After that, the Rockies and much of the central U.S., which have experienced only intermittent hot spells this summer, will bake under more consistent heat later this week.
Little sustained relief from the heat is in the forecast for the next few weeks, as the heat dome, driven by strong high pressure, continues to show staying power into at least the early part of August. The seasonal monsoon, which traditionally provides relief from the summertime heat in the Southwest, could be delayed or weaker than usual, according to AccuWeather's team of long-range meteorologists.
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People walk along a trail as the sun sets, Sunday, July 16, 2023, in Death Valley National Park, Calif. |
Since June, hundreds of temperature records have fallen from Arizona to Texas, and more will be in jeopardy to close out July.
Among the more notable records, Phoenix's run of days in which temperatures reached at least 110 degrees will exceed two dozen on Monday, which is also already above the historical average for an entire year. Meanwhile, El Paso, Texas, hasn't had a day with a high temperature below 100 in over four weeks, also a record.
"The heat dome will continue to contract westward on Sunday, becoming centered over Arizona," said AccuWeather Senior Meteorologist Joe Lundberg. "This will perpetuate the extreme heat in the Southwest."
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Widespread triple-digit temperatures will continue to be common in numerous places such as Phoenix and El Paso, as well as other cities in the region. Even Los Angeles, which has experienced below-average temperatures to begin summer, will begin a run of 90-degree afternoons later this week.
Little relief in the form of cooler air will be felt at night, making the heat particularly dangerous. On Wednesday morning in Phoenix, forecasters said that the temperature failed to drop below 97 degrees. This established a new record for the all-time highest minimum temperature in the city. The old record of 96 was set 20 years ago on July 15, 2003.
While the heat has been constant in the Desert Southwest, the Rockies and most of the Plains have avoided long stretches of intense heat this summer. However, that will change in the coming days, according to AccuWeather forecasters.
"The heat dome will first expand northward up through the Rockies," added Lundberg. "This will spread heat into parts of Idaho, Wyoming and Montana."
Since the beginning of June, Cheyenne, Wyoming, has recorded temperatures that have been below the historical average for that time frame, but that will change beginning Sunday. Afternoon highs will be in the 90s most days into the new week, some 5 to 10 degrees above historical averages.
Residents in the Plains will be next up to feel the effects of the stifling heat.
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"The heat will expand into the Dakotas as early as Sunday, and then arrive over the rest of the Plains Monday and Tuesday before lasting deep into the week," said Lundberg. "Triple digits will be commonplace as far north as North Dakota, especially during the midweek period."
As of Sunday, Wichita has recorded only four 100-degree days so far this summer. That number could be doubled by the end of the week and perhaps tripled by early August. On average, there are 12 100-degree days each year in Wichita.
While the extreme heat can be dangerous for outdoor activities, there are some silver linings to the warmup.
"The expansion of the heat dome will cut back significantly on the episodes of severe thunderstorms and flooding that have become frequent in recent weeks," stated Lundberg.
Many residents in the Southwest may be wondering when the extreme heat will break. Normally, the seasonal monsoon provides relief in the region, but it hasn't been anywhere to be found so far this summer.
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The North American monsoon brings an uptick in cloudiness and rainfall that suppresses the heat and typically runs from June 15 to Sept. 30, according to the National Weather Service's definition. AccuWeather's team of long-range forecasters continues to expect a delayed arrival of that monsoon.
"This year's summer monsoon will be weaker and start later," said Lundberg. "There has been some spotty storms so far this year, but none of the activity has been organized, and the monsoon, when it arrives, will not be as strong or wet as the last two years."
Until that happens, temperature records will continue to be broken.
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