More than a third of Americans are under heat alert early this week as a monster heat dome stifles a huge swath of territory across the central United States, threatening the hottest temperatures of summer. As officials warn of “life-threatening” conditions, numerous records in parts of the Midwest could be reached as the heat continues to pummel the South.
Excessive-heat warnings stretch from Texas and Louisiana to Wisconsin and Minnesota, including the entire states of Iowa and Missouri. Cities under excessive-heat warnings include Des Moines, Kansas City, Oklahoma City, Dallas and Little Rock. Combinations of heat and humidity will lead to feels-like values of 110 to 120 degrees across much of the Midwest and South, with some spots even surpassing those marks.
That already happened Sunday, with heat indexes in numerous locations topping 120, focused on Kansas, Iowa and Missouri.
More than 200 long-period record highs were set since Friday alone, including an all-time high of 112 degrees in College Station, Tex. Another all-time high was reached in Alexandria, La., where it reached 110 on Saturday. August records were set in Abilene, Tex., at 111, and in Stephenville, Tex., at 110.
“The prolonged nature of the heat wave combined with very warm overnight temperatures will limit relief from the oppressive daytime heat and compound overall heat impacts,” wrote the National Weather Service’s Weather Prediction Center early Monday.
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Indeed, several hundred more record highs and perhaps twice as many record-warm lows are forecast through Friday, including the potential for more monthly or all-time high marks. In the Midwest, the hottest temperatures are expected to shift somewhat eastward over the next several days, bringing record or near-record highs to Minneapolis, Chicago, Memphis and Indianapolis, among other cities.
Intense heat ramps up
Heat indexes surpassed 120 degrees in more than a dozen locations across Kansas, Missouri and Iowa on Sunday. In Lawrence, Kan., the heat index reached 134 degrees, from a temperature of 102 degrees and a dew point of 84 degrees. A location in Iowa also recorded the same heat index, but its observations appeared to be corrupted.
“These conditions are untenable for even short durations,” wrote the Weather Service in Kansas City on Sunday.
Looking to put the current heat into perspective, the Weather Service office pointed to a mid-July 1995 heat wave that killed hundreds in Chicago alone.
“Cancel or reschedule activities or move them inside. This is life-threatening heat and any and all precautions should be taken,” it wrote.
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The breathtaking temperatures are thanks to a high-pressure heat dome with little precedent in strength. On Sunday evening, a weather balloon released from Topeka in northeastern Kansas recorded one of the highest known U.S. measurements for high-pressure intensity.
“Never have measurements captured a hotter troposphere over the Central U.S.,” wrote NASA atmospheric scientist Ryan Stauffer.
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To start the week Monday, record highs are set to be threatened from Nebraska to Texas and into the South.
Denver is forecast to reach 99, which would top a record of 97 for the date. Other cities that are expected to break records include Wichita and Dallas, with highs of 106, as well as Shreveport, La., with 105 and Jackson, Miss., with 104.
On Tuesday, record heat potential expands, moving into Minneapolis, with a forecast of 99; Chicago, where temperatures are expected to reach 98; and St. Louis, where the forecast is 102. Another large group of records is anticipated from Texas and eastward, where the heat seems never-ending. Austin is up to 44 days in a row at or above 100, a streak that may persist into September.
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Similarly expansive extreme heat is expected Wednesday. Records are likely in a region focused on Iowa and again across the South. New Orleans will again rise near and past 100, as will Tallahassee.
Thursday may have the largest footprint of record highs, from the lower Great Lakes southward into the mid-South and then the Gulf Coast and Texas. Chicago should spend its third day near 100, with Detroit making the upper 90s, Louisville similar, and then a bunch of records at risk again from Texas into the South.
Amid the slew of record-warm lows, many cities will fail to drop below 80 at night.
By Friday and Saturday, a cold front pushes the record heat farther south and east. Mid-90s in Washington, D.C., could threaten a record Friday, with dozens more at risk south and west of there.
Shifting to the weekend, the main focus is back to the Gulf Coast, where New Orleans could be near 100 through Sunday. The city has already seen 12 days at or above 100, destroying the previous annual record of five days in 1980.
No real end in sight
If you’ve been following the summer heat, you probably know the deal. Rather than abate entirely, a shift of the heat dome toward the southwest United States seems a good bet into the last days of August. Thereafter, it may expand eastward again into September.
A notable cool-down to end the month is a good bet in the Northeast, where several days may end up below average for temperatures. Most other portions of the country remain above to well above average.
Any break in a place like Texas — where heat has been anchored for months — appears quite short, if it lasts at all. Temperatures there look to remain 5 to 10 degrees above normal most of the time through the first week of September.
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