A gradual warmup is in store for the holiday week but the unusual cold will take some time to move out, the National Weather Service said.

A freeze warning was in effect for southern Nassau County until 10 a.m. Monday with overnight low temperatures expected of 23 degrees with gusty winds.

"An impressive arctic air mass has settled over much of the eastern US. Temperatures struggled to rise above the upper 30s [Sunday]," the weather service said, saying Sunday's temperatures and those expected Monday were 10-15 degrees below average.

"Temperatures moderate a bit on Monday, but still remain well below normal in the lower to middle 40s. Lows Monday night will range from the upper 20s inland to the lower 30s at the coast," the weather service said.

The gradual warmup begins Tuesday, which is forecast to be sunny with highs in the upper 40s and an evening low of 33. Wednesday should be even warmer with sunny skies and a high in the lower 50s and an evening low of 35.

Thursday, Thanksgiving Day, will be mostly sunny with a high in the lower 50s, dipping to about 40 in the evening with a 30% chance of rain.

Friday will be warmer and wetter with rain likely and a high in the upper 50s with an evening low about 39. Saturday will be mostly sunny with a high of 50 degrees, the weather service said.