The National Weather Service has issued warnings for a "prolonged, dangerous heatwave" that is expected to intensify across parts of the central and eastern United States over the next few days and into the holiday weekend, bringing record-breaking temperatures, humidity, and dangerous conditions to millions of Americans.
On Thursday, the NWS warned that temperatures between 95°F (35°C) and 105°F (40.5°C), combined with high humidity, will push heat index values across parts of the region to between 100°F (37.7°C) and 115°F (46.1°C). "This will lead to widespread areas of major to extreme Heat risk from the Midwest to the East Coast," the NWS said. "Numerous daily temperature records are expected Thursday, Friday and Saturday, with some monthly and all-time records possible."
Extreme Heat Persists Through Holiday Weekend
The agency said that the extreme heat will intensify across the central and eastern US this week, persist through Friday across the Midwest and Mississippi Valley, and linger through Independence Day weekend across the Ohio Valley and East Coast. Weather officials warned that "prolonged periods of extreme heat are among the deadliest weather hazards" in the US, "because impacts build over time." The NWS advised: "Protect yourself by limiting time outdoors, staying hydrated, and ensuring access to A/C or cooling centers."
As of Thursday morning, numerous areas across the Mississippi Valley, Great Lakes, Ohio Valley, and Northeast are under extreme heat warnings, which are issued when "extremely dangerous heat conditions are expected or occurring."
New York Braces for Dangerous Heat and Humidity
In New York, where temperatures are forecast to climb to around 100°F (37.7°C) on Thursday, weather officials warned that "dangerous heat and humidity" is expected through Saturday, with heat index values forecast to reach "as high as 115°F" (46.1°C). Forecasters also warned that "isolated to scattered thunderstorms are possible each day through Sunday" with the greatest chances from Friday through Sunday. "Any storm has the potential to produce damaging winds, large hail, and localized flash flooding," officials said.
New York City Mayor Zohran Mamdani urged residents to remain vigilant. "Please stay prepared and informed as these dangerously high temperatures continue," he said, adding that Friday's heat index is expected to reach 110°F (43.3°C). "Plan for extreme temperatures. Drink more water than usual. Reach out to vulnerable neighbors who may need help finding resources." Mamdani also announced that the city is deploying cooling vans staffed with medical personnel, who are set to "provide wellness checks, medical care, water and other supplies such as electrolytes and sunscreen, as well as transport to cooling centers or healthcare facilities."
Mid-Atlantic and Washington DC Heat Alerts
Across the mid-Atlantic, forecasters warn that "heat indices up to 110°F (43.3°C) are possible" on Thursday, and said that on Friday and Saturday, afternoon "showers and thunderstorms" are also possible "as heat persists" and "some storms could become severe." Washington DC Mayor Muriel Bowser urged residents to factor the extreme temperatures into their Fourth of July plans. "Consider the heat as you make plans for the 4th of July and America250," she said, before encouraging residents to monitor weather alerts and safety guidance.
Philadelphia and New Jersey: Hottest Days Expected
Weather officials for parts of New Jersey and the Philadelphia area said that Thursday and Friday are expected to be the hottest days of the week there, but warned that "dangerous heat will continue through Saturday." In Philadelphia, organizers shortened the route for the city's "Salute to Independence Semiquincentennial Parade" due to the extreme heat.
Boston EMS Sees Spike in Heat-Related Calls
Emergency responders in Boston are reminding residents that "extreme heat can affect anyone – not just older adults or people with underlying medical conditions." "During a heat wave, Boston EMS typically sees a 10–15% increase in 9-1-1 calls, with patients of all ages experiencing heat-related illness," they said. "So, stay somewhere cool, drink plenty of water and we're here if you need us."
Global Context: Heatwave Follows European Record Temperatures
The heatwave in the US comes just days after parts of Europe endured unprecedented, record-breaking high temperatures, which brought dangerous conditions to parts of the continent.
