Long Island weather: Cooler and less humid today, but also rainy

Saturday’s markedly cooler and breezier air, with a daytime high of 78 degrees and lower humidity expected in the afternoon, will be a welcome contrast to the last few days of tropical-like heat.

Still, a cold front moving south through the tri-state area Saturday could deliver a few heavy downpours and thunderstorms, possibly triggering what the National Weather Service called nuisance and urban flooding. That risk will ease as the morning wears on.

A flash flood warning for parts of Long Island ended at 7 a.m. but a flash flood watch remains in effect until 11 a.m. for New York City, northeast New Jersey, Rockland County and southern Connecticut.

And the soonest Ida, now expected to make landfall near New Orleans as what the National Hurricane Center calls "an extremely dangerous major hurricane" on Sunday — the 16th anniversary of Hurricane Katrina — could bring "heavy rainfall" to Long Island is Wednesday to Thursday, the experts said.

Some relief, then humidity returns

There is a 20% chance of showers Saturday night.

Sunday should be mostly sunny, with a daytime high of 79 degrees.

That pleasant forecast partly stems from a cloud-clearing high pressure system swinging down the New England coast.

"More sun is expected across eastern areas, with more cloud cover anticipated further west," the weather service said.

Then the cold front, transformed into a warm front, will return north.

That means the humidity will rise later Sunday, and there is a 30% chance of showers and storms Sunday night, the weather service explained. And thanks to that front, the weather service said, "expect temperatures to warm up again."

On Monday, thermometers could climb back up to the mid- to upper 80s and even the 90s in spots, such as northeast New Jersey, where heat indices could rise as high as 99.

On Long Island, Tuesday’s daytime high could reach 85 degrees.

Both Monday and Tuesday may see showers and storms, with the odds of rain ranging from 20% to 30%.

What impact the remanants of Ida will have on Long Island hinges on how it interacts with a cold front that on Tuesday should drift south, becoming "nearly stationary somewhere south of New England into the mid-Atlantic region," the weather service advised.

It added, "There will be the potential for heavy rainfall depending on the placement of this frontal boundary."

Wednesday’s odds of showers and thunderstorms were estimated at 50%. Thursday’s odds are 40%.

High temperatures from Wednesday to Friday will top out in the upper 70s, with night time lows sliding to the mid-60s.

Thursday night’s clouds should clear away by Friday, when the sunshine should return as a high pressure system, with falling, drying and cooling air, should push that stationary front out to the south and east, the weather service said.