With temperatures expected to plummet into the 30s tonight, the National Weather Service has issued a frost advisory for most of Connecticut.

The advisory is in effect from midnight to 9 a.m. Saturday for northern Fairfield and New Haven counties and all of Litchfield, Hartford, Tolland, Windham Middlesex and New London counties.

“Frost could kill sensitive outdoor vegetation if left uncovered,” the NWS says. “Take steps now to protect tender plants from the cold.”

With temperatures in the low 40s tonight, only the immediate western Long Island Sound shoreline is safe from a frost.

Far inland areas like Litchfield, Torrington and Litchfield will have temperatures in the low 30s.

According to the NWS’s hourly forecast, temps will drop more than 20 degrees from Friday’s highest temperature. The biggest drop will between 5 and 8 p.m. when the temperature along the shoreline will fall from 65 to 56 degrees between 5 and 8 p.m.

Before the big chill down, expect strong winds on Friday. Strongest winds, as high as 26 mph, are expected between 3 and 7 p.m.

“Low pressure passing east of Nantucket early this morning will move farther out to sea today, while a cold front approaches from upstate and moves across this afternoon,” the NWS says.

“This combination will result in a developing northwest breeze, gusting over 30 mph at times. Temperatures should manage to rise quickly into the 60s this morning, then remain steady or slowly fall during mid to late afternoon with the cold frontal passage.”

Last year, the first widespread frost across Connecticut was Oct. 18.

The forecast

Today: Cloudy through mid morning, then gradual clearing, with a high near 63. Light and variable wind becoming northwest 11 to 16 mph in the morning. Winds could gust as high as 26 mph.

Tonight: Areas of frost after 5 a.m. Otherwise, clear, with a low around 34. North wind 5 to 10 mph, with gusts as high as 21 mph.

Saturday: Areas of frost before 10 a.m. Otherwise, sunny, with a high near 60. Northeast wind 3 to 7 mph.

Saturday Night: Increasing clouds, with a low around 40. Light southeast wind.

Sunday: A 20 percent chance of showers after 9am. Mostly cloudy, with a high near 68. South wind 5 to 10 mph.

Sunday Night: A 30 percent chance of showers. Mostly cloudy, with a low around 59.