Heat wave forecast to set records across much of U.S. through July 4

A large heat dome is forecast to cover more than half the United States through the July Fourth holiday weekend, with heat indices reaching 100 to 115 degrees from the Midwest to the East Coast. Daily highs combined with warm overnight lows are expected to produce more than 300 record temperatures by Saturday, according to forecasters.

Temperatures are projected to run 20 to 30 degrees above average in many areas.

cities prepare New York City Mayor Zohran Mamdani warned residents of extremely dangerous conditions and said the city could reach triple-digit readings Thursday and Friday. The city is deploying vans staffed with nurses and paramedics to distribute water, electrolytes and sunscreen while conducting wellness checks and transporting people to cooling centers.

Washington, D.C., faces an extreme heat watch for Thursday and Friday with a forecast high of 103 degrees. A high of 101 is expected on Saturday, which would exceed the previous record of 100 degrees set for that date in 1919. D.C. Mayor Muriel Bowser urged residents and visitors to plan ahead, stay in the shade and limit outdoor time during the city's 250th anniversary celebrations.

Health risks and western fires Heat is the leading cause of weather-related deaths and poses particular risk to the elderly. Doctors advise watching for fatigue, light-headedness, muscle cramps and upset stomach as signs of heat exhaustion, and altered mental status as an indicator of heat stroke.

In the West, dry conditions and high winds have prompted red flag warnings in parts of Utah and southern Colorado due to active wildfires.