Ontonagon, MI 49948 Frost Dates
Ontonagon, MI: when does the frost end?
Typically, the last spring freeze lands around 05/23, roughly 268 days out. Fall's first freeze usually shows up around 10/01, roughly 128 days after the last spring frost.
Ontonagon sits in USDA Zone 4b (-25 to -20°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
With roughly 5 weeks until Ontonagon's first fall frost, a row cover or cold frame is what stretches the last few weeks of harvest here.
Why 05/23 isn't a guarantee
05/23 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 05/06 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 06/08 and only about 1 year in 10 sees frost after that.
Ontonagon against the rest of the dataset
At roughly 128 frost-free days, Ontonagon places 38,549 of 40,283 ZIP codes in this dataset. Within MI, it ranks 1,049 of 1,153.
Learn more
Before leaning on 49948's figures: local microclimates explains what one yard in Ontonagon can differ from the 49948 normal, while zone vs. frost date explains why Zone 4b and Ontonagon's frost date answer different questions.