Long Island weather: Flash flood watch, heat advisory for Nassau

A heat advisory is in effect until 8 p.m. Saturday for Nassau County, according to the National Weather Service, while Nassau was also put under a flash flood warning from Saturday afternoon through Saturday evening.

Under the heat advisory the weather service advises people to stay cool with air conditioning, either at home or at some other place that has air conditioning. It also says people should check on vulnerable relatives, friends and neighbors.

Saturday afternoon, showers and thunderstorms are expected for most of Long Island, as temperatures will reach near 86 degrees for part of the day, the National Weather Service said.

The rain is likely to hold off until after 2 p.m., when the odds increase to 40%, the weather service said. On Sunday, there’s a 30% chance of showers and daytime highs in the low 80s are predicted for both days.

Western Suffolk County's heat advisory expired at 8 p.m. Friday.

"Sunday, the overall chances of rain are lower, but it’s still likely, 30 to 40% chance, of picking up showers and thunderstorms," said John Cristantello, a meteorologist with the weather service.. "Overall, it looks like Saturday is shaping up to be the rainier of the two days."

And the coming days do not look like record breakers.

"Temperatures will remain near seasonal levels Monday night through Thursday," the weather service said. Highs are expected to be in the low to mid-80s.

The maximum temperature in Islip during July is 81.7 degrees, the minimum is 66 and the mean is 73.9, according to weather service records that begin in 1963.

Only Tuesday and Thursday of next week are not expected to see rain, the weather service said.

Air quality health warnings for high levels of ozone, which can damage lungs, were in effect Friday until 11 p.m., according to the state Department of Environmental Conservation, which issued the alert for Long Island and New York City.

For anyone heading into New York City, a heat advisory will remain until Saturday at 8 p.m., the weather service has advised, adding that a flash flood watch will be in effect from 2 p.m. Saturday until Sunday at 6 a.m.