Frost Dates for 49849 — Ishpeming, Michigan

Half of springs at Ishpeming Wwtp, MI see their last 32°F night by May 26; only one in ten is past it by May 10, and one in ten still has one after June 8. Planting tender crops after May 31 leaves a 30% risk of a frost on them, after June 3 20%, and after June 8 10%. The 13 days between the even-odds date and the one-in-ten date is narrower than at 95% of the 172 Michigan stations behind this site's ZIP pages.

In fall the first 32°F night comes by September 25 in half of years, as early as September 4 one year in ten, and holds off past October 9 one year in ten. A hard freeze of 28°F follows 12 days later, around October 7; in spring the one-in-ten date for 28°F is May 27, 12 days before the 32°F one. The freeze-free season lasts 119 days in a typical year, shorter than at 94% of the 172 Michigan stations; it reaches 141 days one year in ten and falls short of 95 one year in ten. On average 191 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 10 days longer, to about June 5, and return around September 9. Severe cold of 16°F or below comes every winter, usually between November 13 and April 12.

July is the warmest month at Ishpeming Wwtp, MI, averaging 78°F by day and 53°F at night; January is the coldest at 22°F and 6°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 29% of years.

Warmth for growing adds up to 1,612 growing degree days a year (base 50°F), fewer than at 95% of the 172 Michigan stations. 29% of them (465) have built up by the end of June, and July adds the most, 474. Precipitation totals 30.3 inches a year, most in July (3.9") and least in March (1.2"); May to September bring 53% of it.

The nearest other station, Marquette, MI, 10 miles northeast of Ishpeming, has a last frost 4 days earlier (May 22), a first frost 4 days later (September 29), a season 10 days longer.

The first measurable snow (0.1 inch or more) in Ishpeming usually arrives around October 25, and the last of the season around May 2. Those are the middle dates across the winters of 1991–2020 at Clarksburg, MI, 6.3 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 24 days after the last snow.

ZIP 49849 is 3 miles from Ishpeming Wwtp, MI, which stands at 1,406 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 49849 in zone 4b, the band where the coldest night of the year averaged -25 to -20°F (-31.7 to -28.9°C) over 1991–2020; a zone describes winter lows, not frost dates.