A significant and dangerous heat wave is currently impacting more than two dozen states, extending across the Midwest, South, and East Coast, with extreme temperatures expected to continue through the Fourth of July holiday weekend. The heat wave, which began earlier in the week in the Midwest, has spread eastward, bringing prolonged periods of dangerous heat.
The intense heat has already caused disruptions to holiday travel. Amtrak canceled over a dozen trains in the Northeast on Thursday due to concerns about the extreme temperatures affecting infrastructure.
High heat index values, which combine temperature and humidity to indicate how hot it feels, are forecast across multiple major cities. On Thursday, Philadelphia and Washington, D.C. are expected to experience a heat index of 111 degrees Fahrenheit. Boston is forecast to reach 106 degrees, Chicago 102 degrees, Detroit 108 degrees, and Nashville 110 degrees. New York City's heat index is predicted to hit 110 degrees, a level that has only been reached three times in the past 80 years.
In response to the anticipated extreme heat, New York City has activated its heat emergency plan and is opening hundreds of cooling centers. Mayor Zohran Mamdani urged employers to plan ahead, build flexibility into work schedules, and ensure employees are not put at risk during the dangerous conditions.
On Friday, the forecast indicates continued high heat index values, with New York expected to feel like 108 degrees, Boston 105 degrees, Washington, D.C. 112 degrees, and Memphis, Tennessee 111 degrees. Overnight temperatures are expected to offer minimal relief, exacerbating the danger posed by the prolonged heat.
The heat is forecast to moderate slightly for the Northeast on the Fourth of July, but temperatures will still feel like the triple digits, with New York City expecting a heat index of 103 degrees and Washington, D.C. 107 degrees.
By Sunday and Monday, the most intense heat and humidity are expected to shift towards the Southeast. Cities like Raleigh, North Carolina, could experience a heat index of 107 degrees, while Savannah, Georgia, may feel like 105 degrees.
Extreme heat is identified as the deadliest weather-related hazard in the United States. According to data from the Centers for Disease Control and Prevention, at least 13,000 Americans have died from heat-related causes since 2018.