Portland, ME 04108 Frost Dates
04108, near Portland, ME: the frost window
The last spring frost here typically falls around 04/26, about 241 days from today. Fall's first freeze usually shows up around 10/15, roughly 170 days after the last spring frost.
Portland sits in USDA Zone 6a (-10 to -5°F average annual minimum). The dates above are NOAA's 1991-2020 normal at the nearest reporting station, a 30-year average, not a forecast.
Stretching the season past the first frost
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.
Portland against the rest of the dataset
At roughly 170 frost-free days, Portland places 28,886 of 40,283 ZIP codes in this dataset. Within ME, it ranks 120 of 456.
Learn more
Two guides worth reading on 04108: zone vs. frost date, on why Zone 6a and Portland's frost date answer different questions, and the frost range, on how to read the range around Portland's dates instead of trusting one.