The misery index will be off the charts along the East Coast on Sunday, forecasters say.

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Triple-digit heat forecast for a large swath of the U.S.

Heat and humidity will be particularly oppressive in the mid-Atlantic states

CNN  — 

It’s days like these that make you appreciate why Willis Haviland Carrier deserves a spot on Mount Rushmore.

With triple-digit heat indices across a large swath of the U.S., the man who’s credited with inventing modern air-conditioning holds a special place in the hearts and homes of the some 70 million Americans currently under a heat advisory.

Sunday will bring scorching hot temperatures and steamy humidity to much of the country’s midsection and the Pacific Northwest, but it appears the misery index will be off the charts along the East Coast, and around Philadelphia in particular, where the heat index is expected to hit 110 degrees Sunday.

The National Weather Service issued an excessive heat warning Sunday in southeastern Pennsylvania, warning that “the excessive heat and humidity will become a danger if proper precautions are not taken.”

“The combination of hot temperatures and high humidity will create a situation in which heat illnesses are possible,” NWS warned.

And if any of the 6 million folks who reside in the Philly metro area are thinking about packing up the car and heading down the shore, it’s not going to be much better there.

“Sunday will be the most uncomfortable day of the summer so far,” said New Jersey state climatologist David Robinson. Jersey shore beachgoers can only expect a little sea breeze relief, according to Robinson.

It’s not just uncomfortable. Robinson says the oppressive mid-Atlantic heat is downright dangerous.

“Nighttime temperatures are still in the 70s and even the 80s, so the body won’t even have a chance to recover,” he explained. “That’s when you start seeing health issues.”

Making matters worse, it looks like the oppressive heat will continue into the week.

“This is the first prolonged bout of humidity of the summer,” said Robinson. “People are going to have to take it easy.”

God bless you, Willis Carrier.

CNN meteorologist Michael Guy contributed to this report