The frost advisory is in place for 4 a.m. to 8 a.m. Monday, the Weather Service said.
Areas of frost are possible across northern Fairfield County and northern New Haven County, as well as Putnam and Orange counties in New York.
Frost may form with overnight temperatures in the mid-30s and possibly falling below freezing.
The development of frost will pose a risk of damage to sensitive outdoor plants. Plants left outdoors may be killed by the frost if left uncovered, the Weather Service said.
Click here to follow Daily Voice Norwalk and receive free news updates.