NEW YORK (CBSNewYork) – Temperatures will climb into the high 90s again Thursday, but the humidity will make it feel even hotter.

Public swimming pools, like the one in Astoria, Queens, were packed Wednesday.

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“Hot and sticky and humid,” one resident said.

Places like City Park in New Rochelle looked more like a ghost town. Youth soccer coach Paul Ellis cancelled practice and sent his players home around noon.

“It’s too hot… The turf field adds maybe 15 to 20 degrees,” he said. “This is probably the first time I’ve had to do this in 10 years.” 

The extreme heat also cleared out classrooms. In Connecticut, several districts left students out early; others, closed for the day entirely.

“There’s no air conditioning in the school. She came home the last couple days very hot and tired,” said mother Corinne Mastrianno. “So I’m very happy that they’re dismissing early today.”

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Even the pro tennis players at the US Open struggled to keep cool. The dangerous temperatures led to a rule change: 10-minute breaks in between sets.

“I definitely wasn’t feeling great for most of the three sets,” Novak Djokovic said.

So far this year, 17 days have registered 90 or above.

That’s not a record, but low temps at night are not dropping as low as they used to. Researchers at Lamont Dougherty Earth Observatory say we may have to get used to days like these.

“If we look at the current sort of once-per-year worst combination of high temperature and high humidity, we think that a couple generations from now, you could experience that combination of temperature and humidity as often as 20 to maybe even 50 days per year,” said associate research professor Radley Horton.

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Don’t forget to dress for the weather, stay hydrated and take breaks in the AC. Click here for more summer heat safety tips.