The National Weather Service has issued a warning that fog is arriving throughout Long Island and will continue to affect the area through the evening.

"The combination of abundant low-level moisture and diminishing winds has resulted in areas of fog. Visibilities will generally be 1-2 miles, but locally dense at 1/4 mile or less … Improvement will be gradual, but will occur more abruptly with the passage of a cold front this evening," the weather service said Wednesday afternoon, warning drivers to exercise caution.

Light rain is also falling, and the temperatures has been unusually warm, in the high 50s and even 60s. The arriving cold front will turn things slightly chillier, although with lots of sunshine, for Thursday and even more so Friday and the weekend, the weather service said.

December’s high temperature is usually quite a bit chillier: The average high is 44 degrees, according to weather service records for Islip that date back to 1963.

Highs should be in the low 50s Thursday but then temperatures over the next week will remain in the mid-40s predicted during the days and around freezing at night.

The skies should clear by dawn on Thursday, and an arriving high pressure system will bring "brisk" north winds with speeds of 15 to 20 mph, the weather service said.

Thermometers will go down into the upper 20s and 30s that night.

"The cold front moves through this evening and into the overnight. This will allow for the area to dry out and become cooler. Any lingering showers are expected to exit the area by midnight. Skies are then expected to clear out by daybreak on Thursday," the weather service said.

Friday’s sunshine will precede clouds on Saturday.

“Light precipitation cannot be completely ruled out” on Saturday, especially for Long Island’s East End and southeast Connecticut, the weather service said.

Sunday’s chances of rain are 30%, thanks to shortwaves — disturbances in the atmosphere that can raise air ahead of them.

How soggy the tristate’s Sunday becomes hinges on how those shortwaves interact with another low pressure system perched over the Canadian Maritimes.

Right now, the weather service said, anticipate “generally plain rain at the coast and a wintry mix inland, mainly Sunday night into early Monday morning.”

At least partly sunny skies return Tuesday and Wednesday, as another cloud-banishing high pressure pattern reaches the New York metro region.

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