Calais, ME 04637 Frost Dates
04637, near Calais, ME: the frost window
Typically, the last spring freeze lands around 05/04, roughly 249 days out. Fall's first freeze usually shows up around 10/10, roughly 157 days after the last spring frost.
The USDA Plant Hardiness Zone Map puts Calais in Zone 5b (-15 to -10°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
Calais's growing season runs out in roughly 6 weeks — a cold frame or greenhouse kit is the usual way to keep cool-weather crops going past the first frost.
Why 05/04 isn't a guarantee
05/04 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 04/24 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/18 and only about 1 year in 10 sees frost after that.
Calais against the rest of the dataset
At roughly 157 frost-free days, Calais places 33,322 of 40,283 ZIP codes in this dataset. Within ME, it ranks 194 of 456.
Learn more
Two guides worth reading on 04637: local microclimates, on what one yard in Calais can differ from the 04637 normal, and zone vs. frost date, on why Zone 5b and Calais's frost date answer different questions.