Frost Dates for 49953 — Ontonagon, Michigan

Half of springs at Ontonagon 6 SE, MI see their last 32°F night by May 27; only one in ten is past it by May 7, and one in ten still has one after June 13. Planting tender crops after June 2 leaves a 30% risk of a frost on them, after June 6 20%, and after June 13 10%. The 17 days between the even-odds date and the one-in-ten date is wider than at 62% of the 172 Michigan stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 1 in half of years, as early as September 14 one year in ten, and holds off past October 16 one year in ten. A hard freeze of 28°F follows 13 days later, around October 14; in spring the one-in-ten date for 28°F is May 29, 15 days before the 32°F one. The freeze-free season lasts 127 days in a typical year, shorter than at 88% of the 172 Michigan stations; it reaches 151 days one year in ten and falls short of 102 one year in ten. On average 175 nights a year drop to 32°F or below. Nights of 36°F, when frost can still settle on leaves in low, open spots, continue 12 days longer, to about June 8, and return around September 17. Severe cold of 16°F or below comes every winter, usually between November 17 and April 7.

July is the warmest month at Ontonagon 6 SE, MI, averaging 79°F by day and 55°F at night; January is the coldest at 25°F and 9°F. A freezing night is all but certain in every month from October to May (a 90% chance or more). From July to August the chance of a 32°F night stays under 10% each month. In spring, June still brings one in 34% of years.

Warmth for growing adds up to 2,020 growing degree days a year (base 50°F), fewer than at 77% of the 172 Michigan stations. 30% of them (606) have built up by the end of June, and July adds the most, 535. Precipitation totals 33.0 inches a year, most in October (3.6") and least in February (1.6"); May to September bring 46% of it.

The nearest other station, Baraga 7NW, MI, 35 miles east of Ontonagon, has a last frost 2 days earlier (May 25), a first frost 8 days earlier (September 23), a season 8 days shorter.

The first measurable snow (0.1 inch or more) in Ontonagon usually arrives around October 30, and the last of the season around April 18. Those are the middle dates across the winters of 1991–2020 at Ontonagon 6 SE, MI, 6.8 miles away: half of years saw snow earlier, half later. Every one of those winters saw snow. The last 32°F night of spring typically comes 39 days after the last snow.

ZIP 49953 is 7 miles from Ontonagon 6 SE, MI, which stands at 790 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 49953 in zone 5a, the band where the coldest night of the year averaged -20 to -15°F (-28.9 to -26.1°C) over 1991–2020; a zone describes winter lows, not frost dates.