Maine planting zones & frost dates

The 2 Maine cities on this site fall in zones 5b, 6a. Last spring frost dates range from Apr 30 in Lewiston to May 1 in Portland.

City	Zone	Last frost	First frost	Population
Portland	6a	May 1	Oct 9	69,568
Lewiston	5b	Apr 30	Oct 13	38,772

Frost dates are 30%-risk dates from the nearest suitable NOAA station. Population: Census Vintage 2024 estimates.