Dangerous heat is peaking today for millions in the central United States as a heat dome in summer’s hottest month lives up to its reputation — but sauna-like conditions are only just beginning for areas farther east.
The heat index — how hot it actually feels given the temperature and humidity — will top out in the 100s from the Gulf Coast to the Midwest Thursday afternoon while it soars above 110 degrees in some parts of the Mississippi Valley.
Memphis, Tennessee, had its hottest day of the year so far on Wednesday with a high of 97 degrees and a heat index of at least 106 degrees. The city could match that intense heat Thursday while just south in Greenville, Mississippi, the heat index could hit 110 degrees. Farther north, Chicago’s high temperature of 94 degrees could come within a degree of its hottest day so far this year.
That same roasting summer heat started creeping into the Mid-Atlantic and Northeast Thursday. High temperatures in the 90s are likely Thursday afternoon as far north as Burlington, Vermont – located about 30 miles from the Canadian border.
The worst heat for the East arrives Friday with high temperatures in the middle to upper 90s expected from Washington, DC, to Boston. These temperatures are up to 10 degrees higher than the typical hottest conditions for this time of year and could challenge the high temperature record for the day in Baltimore, Philadelphia and New York City.
The heat index will reach or surpass 100 degrees for many major metros: Washington, DC, and Philadelphia will feel more like 105 degrees Friday afternoon and Baltimore will feel nearly 110 degrees at times.
Heat remains the deadliest form of extreme weather in the US. Globally, heat waves are becoming more frequent, more severe and lasting longer as the world warms due to fossil fuel-driven climate change.
More than 60 million people in the eastern half of the US are under at least a Level 3 of 4 “major” heat risk on Thursday, with that total jumping to more than 90 million on Friday, according to the National Weather Service.
Heat this severe impacts anyone without access to effective cooling or proper hydration, not just vulnerable populations, according to the National Oceanic and Atmospheric Administration. And for those without air conditioning, staying indoors can become deadly during the hottest parts of the day, the agency warns.
Humid conditions will also prevent temperatures from cooling significantly overnight. It could still be close to 80 degrees in Washington, DC, by sunrise Saturday — nearly 10 degrees higher than a typical low for late July.
When overnight temperatures don’t cool down enough to offer relief for overheated bodies, people are at greater risk for heat-related illnesses. Nighttime temperatures are taking the hardest hit from climate change, warming faster than daytime highs.
Climate change is making this week’s heat wave at least three times more likely for nearly 160 million people, almost half the US population, when compared with a world without fossil fuel emissions, according to an analysis from the climate research nonprofit Climate Central.
The heat dome will shrink Saturday, replaced by more typical, though still very toasty, late July conditions parts of the Northeast and Midwest. Sweltering heat will persist through the weekend, mainly in southern parts of the Ohio Valley and Mid-Atlantic on Saturday and in portions of the Southeast Sunday.
That general trend of a hotter-than-normal South is expected to continue through next week, according to the latest Climate Prediction Center forecasts.
CNN Meteorologist Briana Waxman and CNN’s Luke Snyder contributed to this report.