The sweltering heat felt in the western U.S. is headed to the Northeast with dangerously hot temperatures putting millions of Americans at risk. The National Weather Service warned on Monday that the looming heat dome “could see temperatures topping the century mark” as it’s expected to break records across several cities. 

The National Weather Service says this will be the first significant heat wave of the season, with “the hottest temperatures of the summer” set to hit the Midwest, Great Lakes, Northeast and Mid-Atlantic. For some areas, the temperatures will be so intense that “the longevity of dangerous heat forecasted … has not been experienced in decades.” 

A level four “extreme” risk is forecast for cities in Illinois, Missouri, Indiana, Michigan, Ohio, Pennsylvania, New York and Massachusetts, the service says, meaning that it’s “rare and/or long-duration extreme heat with little to no overnight relief.” At this level, the National Weather Service says that anyone who doesn’t have effective cooling or proper hydration is at risk. Maryland and Washington, D.C. are expected to be at “major” risk. 

Major cities could see higher temperatures than surrounding areas due to the heat island effect, jeopardizing many who don’t have access to shade or cooling systems. 

CBS News senior weather producer David Parkinson said that “hot hot heat is the name of the game this week.” 

Chicago will reach peak warmth on Monday with a real-feel temperature of 97 degrees Fahrenheit, while Cleveland, Ohio, and Rochester, New York, are expected to tie records of 94 degrees Fahrenheit, he said. On Tuesday, at least 24 other records are expected to be broken, including in Vermont, New York and Washington, D.C., while another three dozen are expected to be broken on Wednesday. 

At least 265 million people will be subjected to temperatures above 90 degrees Fahrenheit this week, Parkinson said, a temperature threshold that can be dangerous and lead to heat-related illnesses. Parkinson said that 22 million will be subjected to temperatures over 100 degrees. 

These maps show what’s expected across the region. 

Tuesday temperature forecast 

NWS forecasters expect that much of the Great Lakes, including Illinois, Indiana, Michigan, Wisconsin and Ohio, as well as surrounding states, will see “major” and “extreme” heat risks on Tuesday, leaving people without adequate hydration and cooling systems susceptible to heat-related illnesses. 

Wednesday temperature forecast

On Wednesday, the National Weather Service forecasts that essentially all of the eastern U.S. and much of the south-central U.S. will see temperatures of at least 90 degrees Fahrenheit. Some smaller areas will see triple-digit temperatures in the Northeast and in the Southwest. 

“By Wednesday afternoon, some locations in interior New England could see temperatures topping the century mark, which will break daily records at certain locations,” the National Weather Service says. “Across the Four Corners region, critical fire danger conditions are anticipated today under persistently dry conditions fueled by gusty winds with the approach of the sharp front.”

Thursday temperature forecast

Thursday is expected to be among the worst days for New England, with even Maine seeing temperatures in the high 90s. Boston temperatures will creep toward triple digits while temperatures in New Hampshire are expected to surpass 100ºF. Little temperature relief is expected at night in many places, including in New York, where forecasters say the lows will be reach the mid-70s. 

Even in areas where temperatures don’t rise high enough to warrant an advisory, New York forecasters say the heat index values will be high enough to “necessitate caution.”