WASHINGTON — A dangerous heat wave stretching across much of the central and eastern United States threatened Fourth of July celebrations on Saturday, prompting officials to issue health warnings, expand cooling services and urge millions of people attending outdoor events to take precautions against extreme temperatures.
The National Weather Service said widespread extreme heat warnings and advisories remained in effect across large parts of the Midwest, Mid-Atlantic, Northeast and South, with daytime temperatures reaching the mid-90s to above 100 degrees Fahrenheit in many locations. Combined with high humidity, heat index values were forecast to climb as high as 110 to 115 degrees in some areas.
The agency warned that prolonged outdoor exposure could increase the risk of heat exhaustion and heat stroke, particularly for older adults, children, people with underlying medical conditions and outdoor workers. Forecasters also said unusually warm overnight temperatures would provide little relief in many communities.
State and local governments opened cooling centers, extended public pool hours and increased emergency medical staffing ahead of parades, concerts and fireworks displays expected to draw large holiday crowds. Officials also encouraged residents to stay hydrated, wear lightweight clothing and check on vulnerable neighbors.
The heat coincided with nationwide celebrations marking the United States' 250th anniversary, including major events in Washington, where organizers planned extensive festivities on the National Mall despite forecasts for dangerous conditions. Water refill stations, misting areas and on-site medical services were scheduled to support attendees.
Meteorologists said the prolonged heat wave was driven by a strong upper-level high-pressure system, commonly known as a heat dome, that settled over much of the eastern half of the country. The weather pattern was expected to keep temperatures well above seasonal averages through the holiday weekend in many areas while threatening daily temperature records in several cities.
In parts of the West, authorities also warned that hot, dry conditions heightened wildfire risks during one of the busiest weekends for consumer fireworks, prompting some local jurisdictions to restrict or ban fireworks displays.
Forecasters said dangerous heat was expected to persist beyond Independence Day in portions of the eastern United States, and emergency officials continued to advise residents to monitor updated forecasts and follow local safety guidance as holiday events continued.
