The region is in the grip of an arctic surge, which could bring a dusting of snow to Boston tonight and will keep temperatures well below normal through midweek.

“Nantucket could get up to 4 inches [of snow], and 1 to 3 across Cape Cod,” said National Weather Service meteorologist Charlie Foley. “If it gets into the metropolitan area, it will just be a dusting.”

Today will be sunny but frigid, with highs cresting at 20 degrees and wind chills as low as minus-1. Clouds will appear this evening as temperatures drop to 14 degrees.

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Snow will start falling between 1 a.m. and 8 a.m. Wednesday, but mostly on the South Shore.

Skies will be cloudy through midmorning Wednesday and gradually clear as temperatures rise back into the mid-20s. Temperatures will plunge again to 11 degrees and wind chills to zero.

“Thursday we’ll start to see the warmup,” Foley said.

Temperatures will rise near 30 degrees Thursday, with sunshine throughout most of the day. Clouds will arrive in the evening, helping keep temperatures in the lower 20s overnight.

Highs on Friday should climb to 36 degrees, a normal reading for this time of year. Partly sunny skies will give way to more clouds in the evening, though lows will only drop into the mid-20s.