01:33 - Source: CNN
Worst heatwave of the year arrives for much of the U.S.

Story highlights

Over 120 million people will see temperatures above 95 over the next week

The heat index could reach 115 for places like Chicago, Kansas City and Minneapolis

CNN  — 

Nearly 60 million people across the Northeastern US are under a heat watch, warning or advisory from the National Weather Service as the worst heat wave of 2018 scorches the most populated region of the country.

That number will only increase this weekend as the axis of extreme temperatures shifts toward the big cities of the Northeast.

Nearly 100 million people will see temperatures climb above 95 degrees Fahrenheit this week, with a majority of those residing in the eastern third of the nation.

Over 120 million people in the United States will see the temperature climb above 95 degrees Fahrenheit during the next week.

On Thursday, the extreme heat can be found over the Rockies and Central Plains, with Denver expecting a record high of 103 degrees, the city’s hottest day since it tied the all-time Denver maximum of 105 in late June 2012.

Major heat for Midwest

The Midwest will see its hottest days on Friday and Saturday, when the combination of temperatures in the upper 90s and high humidity will create a heat index of up to 115 degrees for places like Chicago, Kansas City and Minneapolis.

Excessive-heat warnings are posted for much of New York and New Jersey, where high temperatures and humidity “will combine to create a dangerous situation in which heat illnesses are likely,” according to the National Weather Service.

Residents are warned to “drink plenty of fluids, stay in an air-conditioned room, and stay out of the sun,” the agency says.

Overnight low temperatures are expected to dip only into the upper 70s, which will not allow buildings – and the people inside them – much chance to cool off. This lack of overnight cooling has proven to be deadly in past heat waves impacting urban areas.

Unfortunately, not everyone in these northern climates has the luxury of central air. According to the US Energy Information Administration, about 2 million household units across the Midwest do not have air-conditioning equipment.

Overnight low temperatures are expected to dip only into the upper 70s, which does not allow buildings (and their occupants) much of a chance to cool off. It is the lack of overnight cooling that has proved deadly in past Midwest heat waves.

Fortunately, a round of thunderstorms will mark an end to the extreme temperatures for the Midwest on Sunday, limiting the duration of this round of heat.

Northeast heating up

For the Northeast, heat will build into the weekend, with temperatures well into the 90s into next week.

New York City reached 97˚ F on Sunday, its hottest day of the year so far and tying a record for the day set in 2012. Monday and Tuesday will bring more of the same.

Though the temperatures over the Northeast will not reach the extreme highs of the Midwest and Central Plains, the duration of the heat will be significantly longer.

The Northeast will continue to face above-average temperatures until after the July 4 holiday, with only slight chances for afternoon storms as high pressure remains the dominant weather feature.