Frost Dates for 49866 — Negaunee, Michigan

Half of springs at Marquette, MI see their last 32°F night by May 22; only one in ten is past it by May 6, and one in ten still has one after June 4. Planting tender crops after May 29 leaves a 30% risk of a frost on them, after June 1 20%, and after June 4 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 29 in half of years, as early as September 11 one year in ten, and holds off past October 12 one year in ten. A hard freeze of 28°F follows 11 days later, around October 10; in spring the one-in-ten date for 28°F is May 23, 12 days before the 32°F one. The freeze-free season lasts 129 days in a typical year, shorter than at 87% of the 172 Michigan stations; it reaches 149 days one year in ten and falls short of 108 one year in ten. On average 189 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 3, and return around September 14. Severe cold of 16°F or below comes every winter, usually between November 15 and April 10.

July is the warmest month at Marquette, MI, averaging 76°F by day and 55°F at night; January is the coldest at 22°F and 7°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 20% of years.

Warmth for growing adds up to 1,658 growing degree days a year (base 50°F), fewer than at 94% of the 172 Michigan stations. 29% of them (488) have built up by the end of June, and July adds the most, 473. Precipitation totals 36.8 inches a year, most in September (4.0") and least in February (2.2"); May to September bring 45% of it.

The nearest other station, Ishpeming Wwtp, MI, 5 miles west of Negaunee, has a last frost 4 days later (May 26), a first frost 4 days earlier (September 25), a season 10 days shorter.

The first measurable snow (0.1 inch or more) in Negaunee usually arrives around October 16, and the last of the season around May 2. Those are the middle dates across the winters of 1991–2020 at Marquette, MI, 1.9 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 20 days after the last snow.

ZIP 49866 is 2 miles from Marquette, MI, which stands at 1,411 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 49866 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.