A widespread heatwave is expected to blanket much of the United States through the Independence Day holiday weekend, with forecasters warning of dangerous temperatures and high humidity across large portions of the country.
The National Weather Service said on Sunday that “dangerous to record-setting heat” will spread across the eastern two-thirds of the nation in the coming days.
Communities in states including Ohio, parts of North Carolina and the Washington, D.C., area are expected to face particularly hazardous conditions, with older adults, people with respiratory illnesses and other vulnerable groups at the greatest risk.
Meteorologists warned that the combination of soaring temperatures and high humidity will push heat index values—the “feels like” temperature—to between 100 and 110 degrees Fahrenheit in many locations.
The National Weather Service has placed much of the central and eastern United States under Moderate to Major HeatRisk alerts, warning that prolonged exposure without adequate hydration or access to cooling could lead to serious health impacts.
Extreme heat warnings have also been issued for parts of Iowa, Missouri and Kansas.
Forecasters attribute the prolonged hot weather to a powerful heat dome—a weather pattern in which a large mass of hot air becomes trapped beneath a high-pressure system, allowing temperatures to build over several days.
National Weather Service forecaster Bryan Putnam said humidity will make conditions even more dangerous.
“When temperatures reach the 90s or low 100s, that’s already very hot,” Putnam told NPR. “But when you combine that with high humidity, heat index values can climb well into the 100s, and that’s what people will actually experience.”
The heat is expected to persist beyond the July 4 holiday and extend into parts of the western United States, where daytime conditions could feel like 100 to 105 degrees Fahrenheit.
Forecasters also warned that overnight temperatures may remain unusually high, limiting the body’s ability to recover from daytime heat.
Putnam urged people attending outdoor gatherings and fireworks displays over the holiday weekend to remain cautious, even after sunset.
“Temperatures may stay in the 80s and 90s well into the evening,” he said. “Combined with the humidity, it will continue to feel extremely hot. Just because the sun goes down doesn’t mean the danger has passed.”
Health officials recommend drinking plenty of water, avoiding strenuous outdoor activity during the hottest part of the day, checking on elderly neighbors and relatives, and seeking air-conditioned spaces whenever possible as the prolonged heatwave continues.
