An unrelenting heat wave that’s baked the southern United States for weeks is expanding and will cover the most territory of the summer between Wednesday and Friday, swelling into the Upper Midwest and Northeast.
Between 250 and 275 million Americans will face heat indexes of at least 90 degrees, and more than 130 million people are under heat alerts from southern California to Maine, including Phoenix, Dallas, Oklahoma City, St. Louis, Louisville, Washington, New York and Boston.
The heat will affect parts of the Lower 48 that, thus far, have experienced typical or even cooler than average summer temperatures, including much of the zone from the Northern Plains to the Mid-Atlantic.
In Phoenix, where historically severe heat has been entrenched since late June, excessively high temperatures refuse to relent. The Weather Service is warning of a continued “extreme heat risk” after it hit a record high of 119 degrees on Tuesday for the third time this year.
But Phoenix is one of just many cities that can’t escape from beneath the parent “heat dome” sprawled over the nation’s southern tier and which is now bulging northeastward. El Paso has had a record 40 days in a row at or above 100 degrees, and Miami dealt with heat index values topping 100 for 45 days in a row.
Heat stretching from coast to coast
Heat continues in the Southwest
Wednesday will feature continued records across the Southwest, including in Phoenix, where Sky Harbor Airport is expected to spike to a calendar day record of 118 degrees. Tucson, at 111 degrees, will flirt with a record, as well as Albuquerque, which is enduring its hottest July by a wide margin and could make it to 101 degrees.
The Weather Service office in Albuquerque tweeted that the city “has been roasting like Hatch Green Chile” this month.
Phoenix’s record-breaking streak of days at or above 110 degrees has extended to 26, and it’s on pace to set a record for the most days at or above 115 in a single year — 14. It is also poised to become the first large city in America to log a monthly average temperature at or above 100 degrees.
“It’s the intensity and the duration,” said Austin Jamison, a meteorologist at the National Weather Service in Phoenix. “Sure, we’re having high numbers, but consecutively. It’s one thing to hit 119 on a single day, but this is something else.”
Jamison, who grew up in Phoenix, noted that the city has hit 110 degrees every day this month. The lack of a robust monsoon, which ordinarily cools the desert city by delivering moisture, cloud cover and storms, has been a big player in the furnace-like July temperatures.
While the city is accustomed to the heat, high-end heat for an extended period can be dangerous to vulnerable populations.
“Granted, air conditioning is widespread,” said Jamison. “However, not everyone can go from their well air-conditioned house to their well air-conditioned car to their well air-conditioned workplace and back again. You have tens of thousands of people, if not more, who are working outside. You have a growing homeless population.”
The city has opened cooling locations, and Jamison is hoping people take advantage of them.
Central U.S. to bake
Across the central states, triple digit heat will envelop the entire region from Texas to the South Dakota-North Dakota border on Wednesday. Highs in Houston, Dallas, Austin, Oklahoma City, Wichita, St. Louis, Omaha and Rapid City will be all around the century mark.
On Thursday and Friday, the heat will ease somewhat across the northern tier of the Upper Midwest, but the zone from Texas to central Illinois will bake in 100-degree temperatures. Factoring in the humidity, many places will feel another 5 to 10 degrees hotter.
Chicago and Minneapolis will reside just north of the most intense heat but will still see highs in the 90s and heat indexes approaching 100. Wednesday and Thursday will be the hottest days in Minneapolis and Thursday and Friday in Chicago.
Hazardous heat reaches the East Coast
Triple-digit temperatures will also begin to appear on the East Coast by Thursday and Friday. Newark is slated to hit 100 degrees on Thursday, just shy of the record of 101 set in 2005. New York City could tie a record at 98, and Dulles International Airport, just outside of Washington D.C., is likely to establish a new daily record at 99 degrees.
Those numbers could be matched on Friday, with another 98 at Dulles and a 97 degree record-tying high forecast at New York City’s Central Park.
The last time Washington D.C. hit 100 was on Aug. 15, 2016, at Reagan National Airport and on Aug. 12, 2021 at Dulles. While those numbers might be a bit tough to match this time around, technicalities make little difference to those actually dealing with the summertime swelter.
Even Boston, where the average high in late July is around 82 or 83 degrees, could experience an “official” heat wave. There, it’s informally defined as three consecutive days at or above 90 degrees. Thursday looks to be the hottest at 94 degrees, but the 90s should linger through the end of the week.
Some relief from the heat will reach the Northeast on Saturday and the Mid-Atlantic by Sunday.
Heat exacerbated by dangerous humidity
For those outside the Desert Southwest, it’s not just a dry heat — tropical humidity will combine with the exceptional temperatures, making for heat indexes well above 100 degrees.
In Florida, for example, Manatee Bay logged a water temperature of 101.1 degrees at a depth of 5 feet. In addition to potentially being a world record, the sunbaked seas are pouring copious humidity into the air. That’s why Miami is under a heat advisory. On Monday, the heat index hit 108, and it made it to 106 on Tuesday.
Across the Acela Corridor in the Northeast, heat index values of 102 to 108 degrees will be common, with a few 110 heat index values possible by Friday around the nation’s capital.
The humidity in the air will prevent sweat from evaporating off human skin, preventing the evaporative cooling that’s responsible for regulating our body temperatures.
What’s next
The Weather Service’s Climate Prediction Center is calling for continued extra-hot weather into early August, but the heat dome may shift away from the Southwest, allowing the temperatures to cool slightly.
That said, more of the Appalachians, the Ohio Valley and the Southeast could be subjected to anomalous warmth, meaning the heat is far from done.
Aside from a region of cooler-than-average air temperatures along the heat dome’s periphery in the Northeast, as well as a cool spot over the northern Plains, August is projected to be abnormally warm for the majority of the continental United States.
