Just as many trick-or-treaters were revving up, the temperature was chilly — still in the 50s — and getting chillier, forecasters said.

Look for it to head down slowly, she said, reaching the upper 40s by around 8 p.m., said Carlie Buccola, National Weather Service meteorologist based in Upton.

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So, witches, Draculas and Kim Kardashians should dress accordingly.

Temperatures will get much colder later, especially in Suffolk County, where a frost advisory is in place from midnight to 9 a.m. Tuesday, the weather service said. The mid to upper 30s are expected for most places, but the pine barrens could drop to the upper 20s to low 30s.

High pressure settling over Nassau and Suffolk counties is ushering in a chill for late Monday into Tuesday morning.

Tuesday starts cold, with patchy frost and temperatures in the 20s and 30s.

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The morning chill Tuesday gives way to a mix of sun and clouds with daily highs in the upper 50s.