Doctors are warning people to take the heat seriously.
"Find a place to cool off, stay hydrated and make sure you're taking care of yourself," said Dr. Claiborne Childs, Vice President of Medical Affairs at Riddle Hospital, which is operated by Mainline Health.
Childs says the dramatic rise in temperature can catch some people off guard, sending them to the emergency room. The heat can also be especially risky for people who work outdoors, older adults, younger children and pregnant women.
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Heat waves like this one can put people at risk of heat exhaustion or the even more serious condition of heat stroke.
"Heat stroke is when you get to the point where your body temperature has gone excessively high, and that could be a danger to your life," said Childs. "The symptoms people have, you're outside, sweating, feeling hot, feeling lightheaded, feeling dizzy."
Sweating helps cool down the body; therefore, when someone stops sweating, it's a bad sign. The benefits of getting to a pool or splash pad aren't just recreational. Childs says submerging in cool water can help lower a too-hot body temperature.
On Tuesday afternoon, the normally busy running path along Boathouse Row was nearly empty. Philadelphians seemed to be heeding the warning to limit their time in the sun.
Max Lindenberg, of University City, was one of the few people out running in the heat as he trains for a race. He also, though, knows to take cues from his body.
"Slow down, take a walk, rest in the shade, that's all you can do really," he said.
Interactive map: How much hotter will it get where you live?
Dr. Childs says people can get hydration help from what they eat.
"Fruits definitely have higher water content," he said, adding that foods with potassium and some salt can help retain water (though he suggests keeping one's overall diet and health in mind before adjusting salt intake).
Hydration, of course, also comes from what we drink. Child's recommends water with fluids and electrolytes. He advises against consuming a lot of alcohol on extremely hot days.
"It tends to dehydrate you and exacerbate the symptoms you may have from heat exhaustion," he said.
On the steps of the Philadelphia Museum of Art, tourists were soaking up the heat. It made some feel right at home.
"We are French and it's also really hot there," said Marie Girbaud of Paris, France.
The Sierakowski family from Burnet, Texas, said the Philadelphia heat is nothing compared to what they're used to back home. They did, though, take note of the recent East Coast temperature swing, comparing Tuesday's weather to the weather their children had for a recent baseball tournament.
"They played in Cooperstown, New York, a few weeks ago, and it was in the mid to high 60s," said Joshua Sierakowski.
The heat can also make sidewalks especially hot. It's one reason veterinarians advise pet owners not to exercise with their pet during the hottest part of the day.
If you notice your dog is panting excessively, drooling, or seems lethargic, they could be overheated.