Heat-related warnings were in effect across 29 U.S. states on Tuesday as a heat wave continues to grip large parts of the country, affecting tens of millions of Americans from the Midwest to the Eastern Seaboard.

The National Weather Service (NWS) issued alerts urging people to limit outdoor activity, stay hydrated, and seek air-conditioned shelter as heat indices soar above 100 degrees Fahrenheit in numerous regions.

Why It Matters

The NWS warns that “heat related illnesses increase significantly during extreme heat and high humidity events,” and recommends drinking plenty of fluids, staying out of the sun, and checking on relatives and neighbors.

What To Know

States under extreme heat warnings or heat advisories included wide swaths of the Northeast, Mid-Atlantic, Midwest, and South. Areas such as the New York City metropolitan region, the greater Washington, D.C. area, eastern Pennsylvania, and parts of North Carolina and Michigan, faced “dangerously hot conditions” with heat index values in the triple digits.

The heat index—also called apparent temperature—reflects how hot it actually feels to the human body when humidity is factored in with the air temperature, the NWS says.

“Drink plenty of fluids, stay in an air-conditioned room, stay out of the sun, and check up on relatives and neighbors,” the alerts advised.

States under extreme heat warning, which the NWS issues for periods of “very hot temperatures, even by local standards,” included:

• Connecticut
• Delaware
• Indiana
• Maine
• Maryland
• Massachusetts
• Michigan
• New Hampshire
• New Jersey
• New York
• North Carolina
• Ohio
• Pennsylvania
• Rhode Island
• Vermont
• Virginia
• West Virginia

Additional heat advisories, which signal less dangerous but still potentially harmful conditions, were also in effect across:

• Alabama
• Arkansas
• Georgia
• Illinois
• Kentucky
• Louisiana
• Mississippi
• Missouri
• Oklahoma
• South Carolina
• Tennessee
• Texas

What People Are Saying

The National Weather Service said on X on Friday: “Though record high temperatures are expected in the coming days, the duration of the heat as demonstrated by the numerous record warm morning lows will make this period especially oppressive. Couple this with the fact that this is the first major heat wave of the year – when our bodies aren’t acclimated to the heat yet – will make for an especially dangerous period for many.”

NWS New York said on X, Monday: “New record temperatures set thus far today:

“Bridgeport, CT: 93 (previously 91 in 2010)

“Islip, NY: 93 (previously 91 in 1999)

“Central Park, NY: 96 (ties 96 last set in 1888)

“Newark, NJ: 101 (previously 99 in 2024).”

What Happens Next

At the time of writing, the latest extreme heat warnings were set to remain in place until Wednesday.

The NWS issues regular forecast updates on its website and social media channels.