NEW YORK – The first major heat wave of the summer is firing up across the eastern half of the U.S. this week, with major cities along the Interstate 95 corridor like Washington, Philadelphia and New York City flirting with 100 degrees.

The expansive heat dome will have more than 190 million Americans in the East experiencing temperatures above 90 degrees, but it won’t just be the high temperatures that will make people feel miserable. Humidity, too, will soar, with dew points rising into the 70s.

That will make cities like Chicago, Cleveland, Louisville in Kentucky, Nashville in Tennessee and Raleigh in North Carolina feel well above 100 degrees.

HOW TO WATCH FOX WEATHER

The heat has also been record-breaking in the Midwest. Minneapolis, for example, hit 90 degrees on Saturday, and that broke its old record set in 1900. On Sunday, the city hit 96 degrees, breaking its old record set in 1910.

Now, tens of millions of people from the mid-Atlantic to the Northeast and New England will need to prepare for extreme heat to avoid heat-related illnesses that could arise as temperatures soar.

DOWNLOAD THE FREE FOX WEATHER APP

147 million in 28 states under various heat alerts

More than 147 million people in more than two dozen states from the Midwest and Southeast into the Northeast are under some sort of heat alert that will be in effect for the next few days, and all major cities along the I-95 corridor have been included.

Extreme Heat Warnings – the most dire heat alert issued by the National Weather Service – now stretch from Richmond, Virginia, and Washington, D.C., up the Interstate 95 corridor into Philadelphia, New York City, New Haven in Connecticut, Providence in Rhode Island and Boston.

Pittsburgh, as well as portions of West Virginia and New York state from the Hudson Valley to the U.S.-Canada border, are also under Extreme Heat Warnings.

Chicago and St. Louis are also included in the Extreme Heat Warnings.

HUMID HEAT OR DRY HEAT: WHAT IS WORSE?

High temperatures in the upper 90s to near 100 degrees are forecast in New York City, Washington, Philadelphia and Hartford, Connecticut, on Tuesday.

New York City and Philadelphia have not hit 100 in any month since 2012. 

HEAT KILLS MORE AMERICANS THAN FLOODING, TORNADOES, HURRICANES OR LIGHTNING

In New York City, the temperature had only reached 100 degrees in June three times prior, most recently on June 27, 1966. In Philadelphia, it has occurred 10 times before, most recently on June 15, 1994.

From the Gulf Coast to Massachusetts, heat indices will also top 100 degrees, making it dangerous for those working or playing outside without proper hydration or cooling options.

Dozens of record-high temperatures are also in jeopardy of being broken this week.

WHAT IS A HEAT DOME?

New York City opens cooling centers; Boston declares heat emergency

Officials in several communities across the Northeast and New England have urged people to take proper safety precautions as the intense heat begins to build.

New York City Mayor Eric Adams held a news conference on Saturday and warned that the incoming heat wave would be “brutal and dangerous.”

“Extreme heat will not just be uncomfortable and oppressive for New Yorkers,” he said. “It’s going to be brutal and dangerous.”

Adams said that every year, more than 500 New Yorkers die because of hot weather.

“It is imperative that we prepare ourselves,” he said.

WHAT IS AN URBAN HEAT ISLAND?

Connecticut Gov. Ned Lamont echoed those warnings and announced that he has directed the state’s Extreme Hot Weather Protocol to be activated and in effect from noon on Sunday through at least 8 p.m. on Wednesday.

“It looks like we are about to experience our first heat wave of the season, and when temperatures get this hot, people who are most vulnerable, especially those who are of a certain age or who have certain medical conditions, should take the necessary precautions to stay cool,” Lamont said in a news release. “We are working with our partners to get cooling centers open across Connecticut.”

7 THINGS TO KNOW ABOUT SUNSCREEN

Boston Mayor Michelle Wu declared a Heat Emergency for the city through Tuesday due to the heat.

“With this Heat Emergency coming as we kick off the summer season, we ask our community members to please take care and prepare accordingly for the extreme heat,” Wu said in a statement. “City staff are working to ensure that all residents can have a safe and enjoyable summer. Be sure to stay hydrated, take breaks from working outside and regularly check in on neighbors, friends, and family.”

Splash pads have been opened at various parks throughout the city, and city pools have been made available for swimming.

The Boston Public Library will also be available for residents to seek relief from the heat.