More than 62 million Americans are under extreme heat warnings as of Tuesday, according to an update from National Weather Service (NWS), as high temperatures and humidity beset much of the eastern United States.
A tracking website maintained by the federal weather agency reports that 62.4 million people are subject the alerts, which include major municipalities such as New York City and its metropolitan area, Boston, Philadelphia, Detroit, Chicago, Cleveland, Cincinnati, Indianapolis, Nashville, and Milwaukee, as well as Des Moines, Iowa, and Providence, Rhode Island.
A broader swath of the eastern United States is under a heat advisory and extreme heat watch, according to an NWS map.
On its website, the NWS says that under an extreme heat watch, people should be prepared 24 to 48 hours before dangerous heat is possible in a location, while an extreme heat warning means people should “take action,” and that it’s “within 24 hours when dangerous, life-threatening heat is either imminent or already occurring.”
The agency created the new terms and definitions last year, replacing the previously used terms “excessive heat watch” and “extreme heat watch.”
“The [dominant] weather hazard during this week will continue to be dangerous heat across much of central and eastern U.S.,” the NWS said in a U.S.-wide bulletin, adding that “afternoon highs [and] temperatures in the 90s and lower 100s” Fahrenheit are possible across the region.
Meanwhile, it warned that “increasing humidity values will produce peak heat indices between 105–115 degrees across portions of the Midwest and Mississippi Valley through Thursday, and expanding into the Mid-Atlantic and Ohio Valley by late week.”
It noted that warmer overnight temperatures, which will remain in the 70s F, will only provide “limited relief,” leading to a higher chance of heat-related illnesses, namely among people who are vulnerable and people who lack adequate cooling.
Those conditions are set to extend through the Fourth of July holiday weekend in the United States, which is celebrating its 250th anniversary, with World Cup matches from Toronto to Kansas City, East Rutherford, New Jersey, and Philadelphia all feeling the heat.
Some municipalities in the United States issued alerts or statements regarding the hot temperatures. In one instance, Montgomery County, Pennsylvania, a suburb of Philadelphia, sent out a “code red” hot weather emergency on Tuesday morning.
New York City Mayor Zohran Mamdani also announced Monday that the city will “activate hundreds of cooling centers across all five boroughs on Wednesday and intensify outreach to vulnerable neighbors.”
Chicago Mayor Brandon Johnson also noted that an NWS extreme heat warning was issued for the city and that, should conditions deteriorate, his city “will continue to coordinate the City’s response by working with city departments to assist residents and vulnerable populations.”
In New York, Gov. Kathy Hochul said that the “heat is expected to increase Wednesday and Thursday with most of the state experiencing temperatures around or above 100 degrees, potentially up to 110 degrees in some areas,” noting that heat-related illness “is the leading cause of weather-related fatalities in the United States.”
