Extreme heat threatens Fourth of July celebrations across 23 states

Extreme heat tightened its grip on the Fourth of July weekend, with the National Weather Service issuing extreme heat warnings for 23 states and some communities scaling back celebrations as temperatures climbed into the triple digits. Major Northeast cities including Boston, New York, Newark, Philadelphia and Washington, D.C. were among the places facing dangerous conditions. The National Weather Service warned heat indices in some areas could reach 115 degrees.

The heat raised immediate public-safety concerns, from strained power demand to the risk of emergency-room visits as people spent more time outside for parades, fireworks and backyard gatherings during the hottest hours of the day.

The Centers for Disease Control and Prevention says hot days can harm both physical and mental health, and it lists infants and children, pregnant women, adults over 65, people with disabilities, people with chronic health conditions, people with mental health conditions, people without housing or access to cooling, and outdoor workers as higher-risk groups. Extreme heat is the leading cause of weather-related deaths in the United States, according to federal health resources.

NOAA ranked 2025 as the third-warmest year on record globally and the fourth-warmest year on record in the contiguous United States. 2015 through 2025 were the hottest 11 years on record worldwide, according to World Meteorological Organization data.

More than two-thirds of Americans were under heat alerts in 2023, according to the CDC.