Alpena, MI 49766 Frost Dates
49766, near Alpena, MI: the frost window
The last spring frost here typically falls around 05/05, about 250 days from today. Fall's first freeze usually shows up around 10/17, roughly 163 days after the last spring frost.
Zone 6a (-10 to -5°F average annual minimum) comes from the USDA Plant Hardiness Zone Map; the frost dates above are the 1991-2020 normal at the nearest reporting NOAA station for Alpena, not a forecast for this year.
Stretching the season past the first frost
Alpena'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 05/05 isn't a guarantee
05/05 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 04/21 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/21 and only about 1 year in 10 sees frost after that.
Alpena against the rest of the dataset
About 163 days separate Alpena's last and first frost, putting it 31,358 of 40,283 ZIP codes nationally. Within MI, it ranks 514 of 1,153.
Learn more
Two guides worth reading on 49766: zone vs. frost date, on why Zone 6a and Alpena's frost date answer different questions, and the frost range, on how to read the range around Alpena's dates instead of trusting one.