A relentless and intensifying heat wave is expanding across the central and eastern United States this week, bringing well-above-average heat to millions of people from the Midwest to the East Coast and prompting health advisories across several states.
After pushing temperatures to around 100 degrees in parts of Iowa, Minnesota, Nebraska and South Dakota on Saturday, the heat is expected to continue over the Midwest and shift eastward on Sunday.
By midweek, the heat is expected to affect major urban areas, including New York City, Philadelphia and Washington.
“This is the deadliest weather threat we face in New York City — treat it that way,” the city’s Emergency Management said on social media on Saturday. “Don’t wait until you feel sick. Heat builds. It compounds. It kills quietly.”
New York City officials noted that more than 500 residents die prematurely each year from heat-related causes, and they expect oppressive temperatures to persist through at least Tuesday.
In Philadelphia, the Department of Public Health issued a heat health emergency, beginning at noon on Sunday and continuing through Wednesday evening.
Residents were advised to check on neighbors, family members and pets, and to be aware of heat-related illnesses, such as dehydration, heat exhaustion and heatstroke.
Brian Hurley, a meteorologist at the Weather Prediction Center, said the conditions are the result of a heat dome — a high-pressure system that traps hot air, like a lid on a pot, causing temperatures to rise day after day with little relief.
“That’s really going to have a grip on the eastern United States through at least midweek,” he said. “For the East Coast, mid-Atlantic seaboard, Tuesday and Wednesday are going to be the warmest days.”
He added that Monday is expected to be the hottest day for parts of the Great Lakes region, including Chicago, Detroit and Milwaukee.
High temperatures are expected to soar into the 90s and low 100s through Wednesday, while humidity will push heat indexes to near 115 degrees in some areas.
Mr. Hurley said temperatures in New York and New England would be around 20 degrees above average, and around 15 degrees above average for the Ohio Valley and Mid-Atlantic.
“It’s a bit early to see days between 95 and 100 and 100-plus,” Mr. Hurley added. “The other dangerous aspect of this is the fact that it had been relatively cool across a lot of these areas in the East over the month of June and up to this point. So this will be a shock to the system.”
The National Weather Service issued heat advisories and excessive heat warnings across much of the Midwest, Ohio Valley and Eastern United States.
Warnings are in place from Missouri and Illinois to Indiana, Ohio and Michigan, where conditions may persist through midweek. Southern Minnesota, Iowa, Nebraska and South Dakota are also expected to see high heat index values, potentially reaching up to 115 degrees in some areas.
Across the East Coast, excessive heat warnings were in effect for portions of southern New England, including Cape Cod and southern Connecticut, as well as the New York City metro area and Philadelphia.
Nighttime temperatures may remain in the mid-70s to low 80s in cities such as Baltimore, New York and Washington — limiting the body’s ability to cool down and increasing health risks.
“It’s very stressful on the body,” Mr. Hurley said. “You’re not able to cool down, especially if there’s no ventilation. If you don’t have cooling mechanisms at home, it’s hard to get that relief.”
The Weather Service’s HeatRisk tool, which takes into account duration, humidity and overnight temperatures, rates portions of the central and eastern United States at a Level 3 or 4 through at least Saturday, indicating a major to extreme risk of heat related health impacts, especially for vulnerable groups. Level 4 is the highest category.
A cold front is expected to move through the Northeast later in the week, potentially bringing some rain and a drop in temperatures.
“High temperatures are only going to be in the 70s for much of New England, Friday and Saturday,” Mr. Hurley said. “Maybe even lower 70s for some of these areas. So that’ll be actually a little below normal.”
However, he added that conditions are likely to remain above average across the Mid-Atlantic into the weekend, with temperatures in the low to mid-90s.
“It’ll still be hot, but not as abnormally hot,” he said.
Nazaneen Ghaffar is a Times reporter on the Weather team.
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