Scorching, record-breaking temperatures on Tuesday kept many people indoors throughout the metropolitan region, strained the electrical grid and stoked concerns among those who are the most vulnerable to the heat, including older New Yorkers and the very young.

It was 99 degrees in Central Park this afternoon, the hottest June 24 temperature since records started there in 1869. Kennedy Airport recorded the hottest June day since the site was built in 1948, at 102 degrees.

It is the second year in a row that a heat wave has hit the New York City region earlier than usual, as global warming is projected to worsen heat waves and make them more frequent, climate experts say.

“Our warming climate underlies everything,” said David Robinson, the New Jersey state climatologist and a geography professor at Rutgers University. “It’s not about the highest temperature; it’s about how long it stays hot and the area of coverage of that heat. It’s 100 up in New England today and down here as well.”

Of the 69 weather stations in New Jersey, Mr. Robinson said, over 30 hit 100 degrees. He added that the 10 hottest summers on record for the state had all occurred since 2005.

As climate change wreaks havoc with the traditional calendar, the familiar rhythms of the seasons have begun to shift. New York City pools, for example, are not scheduled to open for the summer until Friday.