Temperatures expected to drop below freezing tonight

By Melissa M. Werthmann, Globe Correspondent

New Englanders should keep extra blankets handy tonight, as temperatures will plummet below freezing, according to the National Weather Service.

The weather service has issued a freeze warning for the region from 2 a.m. to 9 a.m. Saturday.

“You’ll really notice it during the overnight hours because that’s when the cold air is really going to start pouring in,” said meteorologist Alan Dunham.

Saturday will be sunny and cool and Sunday will be warmer, with temperatures rising to the high 60s.

The frigid temperatures tonight will kill sensitive plants and could bring an end to the growing season, according to the weather service.

People are encouraged to harvest or protect tender vegetation and to cover outdoor potted plants or bring them inside.

The low temperatures could also stop mosquito activity.

“Once a hard frost has occurred in an area, virtually all mosquitoes are killed off,” State Public Health Veterinarian Catherine Brown said Thursday in a statement. “The risk of [Eastern equine encephalitis] becomes negligible once a hard frost has occurred.”

Brown said a small risk for West Nile virus remains and that cases have been reported after a hard frost because a few species of mosquitoes that carry the virus move indoors to wait out the winter.

Frost will blanket coastal areas of the Bay State overnight. The weather service has issued a frost advisory for Norfolk, Plymouth, and Suffolk counties.

The coldest temperatures will be in southwestern New Hampshire and areas in northern Massachusetts along Route 2, Dunham said.

The Connecticut River Valley, including Franklin, Hampshire, and northwestern Worcester counties, will have to face temperatures in the low to mid-20s, Dunham said.

Areas along Route 128, including Brockton, Taunton, and Attleboro, will see temperatures in the upper 20s, he said.

Boston won’t be spared from the wintry weather and will have to brave temperatures in the low 30s.

“You’ll be right around that freezing point,” Dunham said.

The city will see temperatures in the mid-50s today, according to the weather service.

A cold front moving through the region could produce some showery rain this afternoon, Dunham said. “The front is marching across the state as we speak,” he said.

Behind the front is “post-frontal precipitation,” a pocket of moisture that could cause brief rain. The wet weather will “last into the late afternoon but most of the precipitation is light and then skies will clear out by this evening,” Dunham said.

A high pressure system will move in right behind the cold front tonight and bring the icy temperatures into the state.

The sun will be big and bright Saturday, but temperatures will only climb to the mid-50s, according to the weather service.

There is a chance of showers overnight Saturday and temperatures will get as low as 45 in Boston.

The chance of rain continues into Sunday morning and temperatures will climb to 68, according to the weather service. The day will be breezy and winds will gust up to 30 miles per hour.

Sunday night will be mostly cloudy and temperatures will be near 60.