Visitors admire scarecrows at Stony Brook Village’s 32nd annual Halloween Scarecrow...

Visitors admire scarecrows at Stony Brook Village’s 32nd annual Halloween Scarecrow competition. Credit: Newsday/John Paraskevas

Crisp fall weather is in the offing this week, with temperatures a bit below normal before moderating toward week's end, the National Weather Service said.

After a day that topped out in the high 50s, clear skies, dew points around 30, and lows in the 40s means frost could be possible for some areas of Long Island Tuesday night, forecasters said.

Wednesday will be mostly sunny, though clouds could form as a weak high pressure system “exits to the east,” the forecasters said. And winds, still coming from the west-southwest, could kick up, gusting to 25 mph.

The daytime high on Wednesday again will rise no higher than the mid-50s, with a low at night of 43, but after that, a warmer trend arrives, raising temperatures to the mid-60s during the days by Saturday.

Thursday will offer more sunshine and slightly warmer temperatures, as the winds shift to the southwest, the weather service said. Highs should be in the upper 50s and lows in the upper 40s.

Another sky-clearing high pressure system will help keep the sun shining through almost all of the weekend with highs in the mid 60s.

On Sunday night, though, there is a 30% chance of showers, “with a potential low pressure system impacting the area to start the new workweek,” the weather service said.

Low pressure systems bring rain as their rising air allows vapors to condense into clouds.

Monday, however, will probably be at least partly sunny.