South Portland, ME 04070 Frost Dates
04070, near South Portland, ME: the frost window
Typically, the last spring freeze lands around 04/26, roughly 241 days out. Fall's first freeze usually shows up around 10/15, roughly 170 days after the last spring frost.
The USDA Plant Hardiness Zone Map puts South Portland in Zone 6a (-10 to -5°F average annual minimum); frost dates are NOAA's 1991-2020 station normal, not this year's forecast.
Stretching the season past the first frost
South Portland's growing season runs out in roughly 7 weeks — a cold frame or greenhouse kit is the usual way to keep cool-weather crops going past the first frost.
Why 04/26 isn't a guarantee
04/26 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 04/16 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/07 and only about 1 year in 10 sees frost after that.
South Portland against the rest of the dataset
At roughly 170 frost-free days, South Portland places 28,908 of 40,283 ZIP codes in this dataset. Within ME, it ranks 122 of 456.
Learn more
Two guides worth reading on 04070: local microclimates, on what one yard in South Portland can differ from the 04070 normal, and zone vs. frost date, on why Zone 6a and South Portland's frost date answer different questions.