Anyone who has already started their spring planting will need to cover up their plants Wednesday night.
Environment Canada has issued a frost advisory for London-Middlesex, Sarnia-Lambton, Elgin County, Oxford County, southern Huron County, Chatham-Kent, and Windsor-Essex as widespread frost is expected to develop as temperatures drops to near or below the freezing mark.
The frosty conditions could damage or destroy some plants, the weather agency has warned.
In order to protect frost-sensitive plants and trees from potential damage, the greenery should be covered with a blanket or burlap. Hanging or potted plants can be tucked away in sheds or brought inside houses.
The advisory is expected to remain in place until early Thursday morning.
The below seasonal overnight low temperature comes a day after a cold front moved across the region. The average low for this time of year is 7 C.
Warmer conditions will return Thursday with sunshine and a daytime high of 21 C and an overnight low of 12 C in the forecast.