Portland, ME 04050 Frost Dates
Portland, ME: when does the frost end?
Around 04/26 is the usual last spring frost, about 241 days away. 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 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
With roughly 7 weeks until Portland's first fall frost, a row cover or cold frame is what stretches the last few weeks of harvest here.
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
Portland's growing season runs about 170 days, ranking 28,884 of 40,283 US ZIP codes measured here, longest to shortest. Within ME, it ranks 118 of 456.
Learn more
Before leaning on 04050's figures: local microclimates explains what one yard in Portland can differ from the 04050 normal, while zone vs. frost date explains why Zone 6a and Portland's frost date answer different questions.