Tens of millions swelter as heatwave blankets the central and eastern US | US weather

The National Weather Service (NWS) has issued several extreme heat warnings and advisories as a dangerous and prolonged wave of high temperatures and humidity blankets much of the central and eastern US, with the worst conditions expected to persist into the middle of this week.

Several locations recorded their hottest temperatures of the year over the weekend: Salt Lake City, Utah, hit 104F (40C) on Thursday, its first triple-digit reading of 2025, and on Saturday the city of Mitchell in South Dakota also reached 104F, surpassing its previous daily record of 101F. Daily high records were broken in parts of Minnesota, Wyoming and Michigan.

Cities under active heat alerts include Chicago, Kansas City, St Louis, Detroit, Cincinnati, Pittsburgh, Philadelphia, Washington DC and New York City. The NWS classified some of its warnings as “extreme heat” alerts, its highest level, due to the severity of the conditions.

Some cities – including Boston, New York City, Philadelphia and Washington – could approach or surpass 100F during the peak of the heatwave. New York’s Central Park hasn’t reached that level since 18 July 2012, the NWS said, while Philadelphia last hit it in June 1994.

Humidity is also a factor, with oppressive moisture levels driving “heat index” values – which factor in humidity to give a sense of how hot it feels to a human – into the triple digits in part of the midwest, Great Lakes, mid-Atlantic and north-east. In some areas of the central US the heat index could reach as high as 115F.

Meanwhile, night-time lows around 70F-80F in urban areas will offer little relief and increase the risk of heat-related illness, particularly among vulnerable populations.

In New York City, officials are encouraging residents to take precautions. “This is the deadliest weather threat we face in New York City – treat it that way,” the city’s emergency management agency warned on Saturday on social media. “Don’t wait until you feel sick. Heat builds. It compounds. It kills quietly.”

The National Weather Service in New York noted late on Monday afternoon that the record high temperature for 23 June in “Central Park has been tied at 96 degrees” and that the “last time 96 degrees was reached on this date was back in 1888”.

Philadelphia’s department of public health declared a heat health emergency starting Sunday at noon.

Officials are urging the public to stay hydrated, limit time outdoors and check on elderly neighbors and others at risk as the heatwave persists.