Temperatures on Long Island hit the triple digits yesterday, with a slightly cooler, but still sweltering day, predicted for today.

Long Island MacArthur Airport hit 100 degrees at 2:50 p.m. Tuesday, the first time since July 22, 2011, and only the eighth time in history since records began in 1963. It was the hottest-ever June day in Islip, according to Newsday TV meteorologist Rich Von Ohlen.

Today is the third day of the region's heat wave before relief comes with storms tonight that usher in highs tomorrow barely surpassing 70 degrees.

Heat indexes, heat combined with humidity, will go as high as 97-102 degrees for much of Nassau and Suffolk today, according to the National Weather Service's heat advisory. Some east end coastal locations will have slightly cooler heat indexes, between 95 and 100°F.

Gov. Kathy Hochul, in a news release last night, said that New Yorkers should set their air conditioning at 76 degrees.

Yesterday, the hottest of this week’s three-day heat wave, saw a recorded temperature of 100.4 degrees at Gabreski Airport in Westhampton Beach as of 2:15 p.m., the weather service said.

According to Newsday's Von Ohlen, some of the other high temperatures Tuesday as of 2 p.m. included: Shirley at 99, Montauk at 97, Farmingdale at 97, and East Hampton at 94.

"This was a perfect, unique setup to get these temperatures," Von Ohlen said. "We did not get the sea breeze that normally cools Long Island ... which is why Montauk saw the upper 90s, which is very rare."

An air quality alert has been issued for Long Island and the metro area from 11 a.m. to 11 p.m. today, when excess amounts of ozone are expected due to the hot weather. The air quality for Long Island Tuesday was considered to be unhealthy for sensitive groups due to the ozone.

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Long Island schools closed early or took other measures to keep students cool yesterday, as temperatures hit triple digits in some areas of Nassau and Suffolk .

The heat wave continues today, with real-feel temperatures around 100 degrees predicted for most parts of Long Island.

Some schools had already scheduled half-days for the rest of the week — the final week of the school term.

Maura McDermott reports in NEWSDAY that many classrooms in schools across Long Island lack air conditioning. A heat wave "definitely impacts the work environment and the learning environment" in those classrooms, said Robert Vecchio, executive director of the Nassau-Suffolk School Boards Association. But, he said, "Schools have always had plans for hot days in June and hot days in September," including the use of misting fans and moving classes to cooler parts of the building.

A new law that takes effect Sept. 1 will require public schools to take action when classroom temperatures climb too high.

The law, signed by Gov. Kathy Hochul in December, mandates that schools take steps such as using fans and pulling down blinds when interior temperatures hit 82 degrees. When room temperatures reach 88 degrees, schools would need to move students and staff to a cooler space or send students home, under the law.

However, Vecchio said the state law also "presents new challenges," especially in areas that are lower-income or have smaller tax bases.

Adding air conditioning "can be very expensive and very complicated due to the size and age of buildings," he said. Without voter approval for massive investments in cooling systems, he said, in some schools the mandate "can lead to...