Most of Long Island will be under a heat advisory...

Most of Long Island will be under a heat advisory on Labor Day with a heat index in the upper 90s, according to the National Weather Service. Credit: Newsday

Most of Long Island is under a heat advisory that won't expire until 9 p.m. Tuesday, according to the National Weather Service.

The advisory covers all but southeast Suffolk County and is followed by more hot days until Friday, the service said.

“Anyone planning strenuous outdoor activity” should take note, said Faye Morrone, meteorologist with the National Weather Service. “It can be dangerous at this level.”

Tuesday's high is expected to be 90, but with the humidity, it'll feel like 96, the service said. On Wednesday, the high dips to 83, but the humidity will make it feel like 89, meteorologists said, while Thursday's high of 87 will feel like 94.

The high temperatures and humidity are expected to last until Friday, when an approaching cold front drops the expected high to 81 degrees, the service said. There's a 40 percent chance of rain during the day, then a 30 percent chance before midnight, meteorologists said.

The weekend is expected to be cloudy, with highs in the low 70s.

With Ellen Yan

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