Having reached the mid-60s Wednesday afternoon, overnight temperatures are expected to dip to the low 40s for most of Long Island, forecasters said.
Frost is also in the picture for some places, they say.
A frost advisory is in effect for areas to the north of Long Island, with the Pine Barrens area also slated to bring frost conditions, the National Weather Service said.
Thursday is predicted to be mostly sunny, with highs of around 60 degrees, and rain getting started in the early hours of Friday.
Friday goes on to see steady rain, moderate to heavy at times, said Faye Barthold, weather service meteorologist, based in Upton.
The bulk of the rain falls during daylight hours she said, with the possibility for thunderstorms in the afternoon. In all, 1.5 to 2 inches could fall from Friday through Saturday, which is expected to bring the chance of off-and-on showers.
There is a small craft advisory for Long Island waters and the New York Harbor from 2 to 11 p.m. Wednesday as wind gusts up to 25 knots and seas could run up to five feet higher, the weather service said.