LI forecast: Sunny, muggy Tuesday with possible overnight storms

The last unofficial week of summer looks to be mostly sunny, according to the National Weather Service, with Tuesday's overnight into Wednesday morning providing the only significant chance at rain this week.

Monday night is looking to be partly cloudy, with a low of about 72 degrees and the chance of some patchy fog. And the high humidity isn't going anywhere soon, forecasters said.

"Another muggy night is ahead with temperatures remaining mild, forecast lows within a couple of degrees of 70 almost everywhere. With the moist flow off the waters and [high dew point] … expecting patchy fog and low clouds to develop once again overnight, lingering into the morning hours," the weather service said.

Any fog that stays around Tuesday morning will burn off quickly and it's expected to be a mostly sunny day with highs in the low 80s.

On Tuesday night, however, there is a 60% chance of rain and thunderstorms overnight. There is a 30% chance the storms will remain in the area through Wednesday morning, but conditions should clear and it is expected to be mostly sunny with a high of 86 degrees, the weather service said, dropping to 66 at night.

Then, right through Labor Day, forecasters expect mostly sunny skies with highs in the mid to high and lows in the mid 60s, with the humidity gradually coming down.

“A cold frontal passage occurs Tuesday night into Wednesday. High pressure then builds in from the west through the end of the week,” the forecast says.

The water at the ocean beaches are at their warmest of the year now through mid-September, said David Wally, a meteorologist based at the weather service’s regional office, which is in Upton.

Long Island will be coolest along the South Shore and warmest in the center of the island and along the North Shore, Wally said. But temperatures could be more equal Islandwide depending on winds.

With Matthew Chayes