After a month of bringing blistering heat to the Southwest, the southern Plains and the Gulf Coast, the relentless “heat dome” that has caused an outbreak of extreme temperatures is about to expand across even more of the country.
The heat over the coming week won’t be as intense as it was in the Southwest last week, but will cover a lot more territory. In other words, on balance, this will be the hottest week of the year so far for the Lower 48.
The heat is forecast to be most pervasive on Wednesday and Thursday, when more than 250 million people in the United States will experience heat indexes — a measure of how hot it feels, factoring in humidity — over 90 degrees. Temperatures are predicted to be above normal in all regions but the Pacific Northwest.
Highs will reach the triple digits from Phoenix to St. Louis and at least the mid-90s from New Orleans to New York.
It comes amid a July that’s likely to go down in the books as Earth’s hottest month in recorded history, and perhaps the warmest in the past 100,000 years. Heat records have been shattered worldwide, posing grave health concerns in regions where air conditioning is hard to come by or economically inaccessible.
In the coming days, the heat dome — or ridge of high pressure featuring hot, sinking air — will grow in size and widen. That will help establish records far and wide as the most intense heat pushes east.
On Monday, the core of the heat remains entrenched over the interior Western United States; records are possible from the Canadian border to Mexico. Kalispell, Mont., where records date to 1899, could hit 97 degrees, a record. Missoula and Helena should hit 101 and 100 degrees, respectively, tying or breaking records. Grand Junction, Colo., should be hot as well at 103 degrees, tying a record.
In the Texas Panhandle, highs on either side of 105 degrees should easily net a few records, while Phoenix will be near its July 24 record high of 116.
Denver, Salt Lake City, Oklahoma City and Wichita are among other cities expected to see highs near the century mark.
Triple-digit heat could expand as far east as Kansas City, Mo., on Tuesday, while more records could fall from the Texas Panhandle westward. Billings, Mont., is forecast to tie a record at 97 degrees, but that pales in comparison with the readings in the Southwest. Phoenix and Tucson should both tie or break records at 117 and 110 degrees, respectively, while Roswell, N.M., could reach near 107 and also nab a record. Amarillo and Lubbock, Tex., should both hit 104, tying or breaking records. Highs will also flirt with records in South Florida.
Wednesday will see the heat ooze into the Upper Midwest. Highs from 95 to 100 degrees will span from New Orleans to northern Minnesota, including Little Rock, St. Louis and Des Moines. Factoring in humidity, many of these areas will feel at least five degrees hotter. Minneapolis could approach its July 26 record temperature of 100 degrees and will have a heat index near 105.
By Thursday, this heat will spread farther east. The 90s will surge through much of the Great Lakes and Ohio Valley, extending into Erie, Pa., a city expected to break a record at 91 degrees. Hagerstown, Md., and Washington, D.C.’s Dulles International Airport should both hit 97 degrees, one degree short of records. To the west, Dallas, Oklahoma City, Kansas City and St. Louis could all hit 100.
On Friday, while the heat eases ever so slightly in the Southwest, it intensifies in the Mid-Atlantic and Northeast, where highs should surge well into the 90s. Dulles Airport is forecast to hit 99, tying a record. It’s possible Washington could see its first triple-digit high since Aug. 15, 2016. Upper 90s are likely in New Jersey and around New York City, while mid-90s line the Connecticut River Valley from Hartford to Springfield, Mass.
As impressive as the magnitude of the heat is its longevity, particularly across the Desert Southwest. Phoenix marked 24 consecutive days at or above 110 degrees on Sunday, shattering the previous record of 18 days, which occurred in June 1974. Records in Phoenix date to 1895. The effects of human-caused climate change, along with the role of urbanization and land use changes, are helping temperatures to routinely reach extreme levels.
Phoenix has also had more than two weeks nonstop with overnight lows remaining above 90 degrees, which doubles the previous record streak of toasty nights. Factored together, the hot lows and the even more scorching highs will probably make July 2023 in Phoenix the first time that any American city has achieved an average monthly temperature over 100 degrees. So far, the average temperature has been 102.7 degrees, the month coming in 7.1 degrees above normal.
On Sunday, Las Vegas hit at least 110 degrees for a record-tying 10th straight day. Salt Lake City has twice in the last week matched its highest average temperature (taking into account daytime highs and nighttime lows) on record.
It’s not just Phoenix, Las Vegas and Salt Lake City that can’t shake the heat. In El Paso, the past 38 days have all surpassed 100 degrees. And in Miami, while the actual air temperatures may not have set records each day, the heat indexes largely have. Miami has seen a record 43 days in a row with a heat index over 100 degrees, 26 of which have been daily heat index records.
The unforgiving heat is closely linked to extremely hot water temperatures off the southwest Florida coast. That’s contributing to exceptional humidity in the air. Sea-surface temperatures in the 90s have been reported between the Florida Keys and the southern tip of the Everglades, which has also resulted in coral reef bleaching.
Sunday also tied the hottest average temperature in Miami’s history, with a daytime high of 98 and a morning low of 82. Only one other day — July 24, 1983 — had the same.
In the extended range, there is no end in sight to the exceptional heat dominating North America. Most heat domes break down after a week or two, but not this one: It looks to remain large and in charge into August.
The Climate Prediction Center continues to portray a likelihood of hot weather predominating over the United States well into next week. An exception may be the Pacific Northwest and parts of the Northeast, where near or slightly below-average temperatures are possible.
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The Washington Post’s Jason Samenow contributed to this report.