CNN —
A long-lasting and expansive heat wave is set to grip the Midwest and Northeast with record-breaking high temperatures through next week, ushering in the start of summer with this year’s most significant heat event yet.
Nearly 200 high-temperature records could be tied or broken this week as a massive heat dome parks over part of the East and may last into early next week. Some areas could endure the longest heat wave they’ve seen in decades, the National Weather Service’s Weather Prediction Center said.
Tens of millions of people who aren’t used to heat this intense will be sweating in temperatures well into the 90s this week.
The heat arrived in the South and Midwest as many families celebrated Father’s Day outdoors on Sunday, prompting caution from the weather service to stay cool amid 90-degree high temperatures in some areas.
Through the rest of the week, the most extreme heat risk is in place from the Great Lakes into the Northeast, according to the National Weather Service. This includes the major metropolitan areas of Chicago, St. Louis, Detroit, Cleveland, Pittsburgh, New York City and Boston.
By Monday afternoon, temperatures will top out 15 to 20 degrees above normal over a sweeping area of the northeastern US and are expected to grow to 25 degrees above normal through the rest of the workweek.
Some areas, including Pittsburgh, haven’t seen heat like this in about three decades.
“Last time we saw heat in Pittsburgh like what we’re expecting next week was 30 yrs ago (almost to the day) when it reached 95°F or warmer for 6 straight days (June 15-20, 1994),” the local weather service office said. “That stands as the longest stretch of 95+ (degree) days on record. We have a shot at tying or beating that.”
Heat domes trap air in place and bake it with abundant sunshine for days on end, making each day hotter than the last. The oven-like conditions mean overnight temperatures often don’t cool down enough to offer relief for overheated bodies, posing increased risks for heat-related illness.
“Warm overnight temperatures only dropping into the mid-70s will offer little to no relief, especially to those without adequate or reliable cooling,” the Weather Prediction Center said.
Humidity will also join forces with extreme heat to create triple-digit heat indices – measurements of how hot the human body feels – in some areas.
Chicago residents could feel heat indices between 95 and 105 degrees through next week, the NWS in Chicago warned. Parts of eastern New York and western New England could see indices as high as 107 degrees.
Heat-related illness is a concern in severely impacted areas, particularly for the elderly, young children and outdoor workers. Extreme heat is by far the deadliest form of severe weather, killing on average twice as many people a year as tornadoes and hurricanes combined.
Scientists have warned that heat waves will become increasingly severe as the climate crisis intensifies.
The NWS in Detroit, where the heat index could reach 100 degrees, urged residents to practice heat safety in the coming days, including limiting strenuous outdoor activities, staying hydrated, and checking up on neighbors who are elderly or don’t have A/C.
CNN’s Robert Shackelford contributed to this report.