There's a slight chance Halloween trick-or-treaters will need umbrellas and rain gear, the National Weather Service said Thursday.
Possible light rain is expected, starting Friday, probably between 3 p.m. and 8 p.m., the service's Upton office said.
There's a 20 percent chance of rain in the early evening hours, followed by a 50 percent chance of rain after 11 p.m. and into Saturday morning.
High pressure building from an outgoing cold front coupled with low pressure in the Atlantic is likely to generate cloudy conditions and the chance of precipitation, the service said.
Thursday conditions should be relatively mild, with mostly sunny skies and temperatures climbing close to 60, the service said.
Nighttime lows are expected to be in the low 40s, with winds out of the northeast from 3 to 5 mph.
For most of Friday, skies should be partly sunny with temperatures ranging from the mid to high 50s, the service said.
Clouds start to appear later in the day, after about 3 p.m., the service said.
Nighttime lows are expected to be in the mid 40s, with northeast winds a bit stronger, between 9 and 16 mph.
By Saturday, the system strengthens, with the chance of rain for most of Nassau and Suffolk counties ranging between 50 and 60 percent.
Daily highs are likely to dip, too, well into the low 50s.