A heat dome forecast to expand across the central United States threatens days of extreme heat with limited overnight relief, driving higher humidity and dangerous heat index levels. Forecasters warn the timing could complicate Fourth of July travel and events
For days, Washington, DC has been preparing for celebration. Next week, forecasters say the city may be preparing for something else entirely: heat that can become dangerous for anyone without reliable cooling.
A developing heat dome is expected to build and expand over the central United States as the week progresses, with daytime highs approaching triple digits for some areas. The system is also forecast to spill into parts of the East for several days, AccuWeather said.
“People who mind the heat will be very uncomfortable if they don’t have air conditioning,” AccuWeather meteorologist Alex Duffus said.
The timing matters. Visitors traveling to mark the nation’s 250th birthday in Washington, DC could face perilously hot conditions, with widespread highs in the 90s and high humidity in the Mississippi and Ohio valleys, Duffus said. At its peak, more than two dozen states are expected to be affected.
Across cities, the heat is likely to hold longer into the night. Urban areas retain warmth from solar energy absorbed by pavement. brick and concrete. and the long daylight hours of June and July can keep overnight temperatures elevated. Forecasters warn that some locations may see overnight lows persist above 80 degrees.
“While there will be a handful of locations that set record highs on a daily basis, there may be many more where record warmth occurs at night,” AccuWeather meteorologist Brandon Buckingham said.
Chicago, St. Louis and Kansas City face a long stretch
In the Midwest. Chicago residents are expected to see highs around 90 degrees for four to five days in a row. AccuWeather said. In St. Louis. where highs are typically in the high 80s this time of year. temperatures are forecast to climb into the 90s for at least eight straight days. approaching 100 degrees.
Kansas City is also in the path, with highs in the mid to upper 90s, according to the National Weather Service.
Humidity is expected to make the heat harder to tolerate. Dew points are forecast to eclipse the 70-degree threshold as moisture climbs. AccuWeather explains that higher dew points mean perspiration is slower to evaporate. making it difficult for the body to cool off. When those conditions persist, the danger of heat exhaustion and heatstroke rises.
Eastern cities could see century-level heat
The heat and humidity are expected to reach Eastern states by midweek, with the impact possibly lingering through the Independence Day weekend, AccuWeather said.
In Philadelphia and Washington, DC, highs could hit 100 degrees for several days—well above their average highs in the mid to upper 80s. New York City could also see temperatures reach the century mark as the weekend approaches, and Newark, New Jersey is even more likely to see triple digits.
For both cities, forecasters say the situation could worsen as humidity and cloud cover interact, with heat indices pushing 110. The region isn’t expected to cool down until sometime during the holiday weekend, according to the weather forecaster.
A separate worry in the Southwest: wildfire conditions
The heat dome is also expected to bring thunderstorms along its edges, with storms tracked from the Rockies to the northern Plains and others forming along the Gulf Coast. AccuWeather said those storms could provide temporary afternoon relief.
But in the short term. the National Weather Service says wildfire conditions remain critical across the Southwest. particularly in the Four Corners area. and in portions of the Great Basin. In a statement from its office in Grand Junction. Colorado. the agency said 40- to 50-mph wind gusts would produce another day of “strong fire behavior. ” with smoke from regional fires affecting air quality and visibility.
By the holiday weekend, forecasters expect a change in the pattern. A shift in the jet stream over the Fourth of July weekend should force the heat dome to retreat to the Plains, finally ushering in cooler air for the sweltering Eastern region.
That shift could bring relief late enough to test anyone caught in the hottest days first—especially people traveling for Independence Day celebrations.
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