Friday will begin with clouds that are destined to thicken, bringing rain by about 4 p.m. — and the first two days of the Memorial Day weekend will also likely be cool and soggy, the forecasters said.

Saturday’s odds of rain are 80% — up from the previous 60% estimate — and Sunday’s chances have doubled to 60%, according to the National Weather Service. At least Memorial Day on Monday will offer a reprieve: sunny skies are predicted with a daytime high of 70 degrees.

Thermometers will top out at 65 degrees on Friday. Saturday's daytime high will be a chilly 57 degrees and Sunday's will be 61, the weather service said. Wind gusts could reach around 30 mph on Saturday and 24 mph on Sunday.

Organizers of the Bethpage Air Show, to be held Saturday and Sunday, say they are prepared for inclement weather.

Up to two inches of rain possible

The rain, with as much as two inches expected to begin falling Friday afternoon through Saturday night, stems from a Midwest low pressure system that will sweep east, imperiling Memorial Day celebrations along the Eastern Seaboard, the forecasters said.

"A low pressure system entering the Ohio Valley this morning is forecast to bring widespread showers and locally heavy rain to the central Appalachians and Mid-Atlantic today," the weather service's Weather Prediction Center said Friday.

It added, "Additionally, thunderstorms are likely to form along and south of an associated warm front that is expected to slowly lift northward across the Mid-Atlantic today."

Severe storms — including high wind gusts, possibly an isolated tornado and hail predicted for parts of Virginia — are not expected to hit Long Island.

"The system is then expected to stall as it reaches the East Coast on Saturday, leaving a stiff northeast wind and light rain to linger through the weekend for the Mid-Atlantic region and Northeast," the prediction center said.

Low pressure systems deliver rain as their air warms and rises, allowing vapors to become clouds and rain drops. High pressure systems can create blue skies because their falling air dries and cools.

On Long Island, there is a high rip current risk that will last through Saturday for southern Nassau and Suffolk, the weather service said.

"Widespread minor coastal flooding is likely with tonight's high tide," the weather service said Friday.

A coastal flood advisory was issued for the South Shore back bays, lower New York Harbor, and western Long Island Sound, the weather service said. Further, a coastal flood statement is in effect for southwest Suffolk, mainly along the western portion of the Great South Bay.

Gale conditions were predicted for much of the waters, except the western Long Island Sound and New York Harbor, which will last into Saturday morning and all day on the ocean, the weather service said.

The work week will resume Tuesday under partly sunny skies, with a high during the day of 74 degrees expected, the weather service said.

Wednesday will be almost precisely the same, but there is a 30% chance of showers that night.

And Thursday has the same odds of precipitation, and the same high of 74 degrees expected.