Frost Dates for 54758 — Osseo, Wisconsin

Half of springs at Augusta Rs, WI see their last 32°F night by May 7; only one in ten is past it by April 23, and one in ten still has one after May 20. Planting tender crops after May 12 leaves a 30% risk of a frost on them, after May 15 20%, and after May 20 10%. The 13 days between the even-odds date and the one-in-ten date is narrower than at 84% of the 182 Wisconsin 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 17 one year in ten, and holds off past October 14 one year in ten. A hard freeze of 28°F follows 10 days later, around October 11; in spring the one-in-ten date for 28°F is May 11, 9 days before the 32°F one. The freeze-free season lasts 146 days in a typical year, shorter than at 73% of the 182 Wisconsin stations; it reaches 165 days one year in ten and falls short of 128 one year in ten. On average 168 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 May 17, and return around September 24. Severe cold of 16°F or below comes every winter, usually between November 13 and April 1.

July is the warmest month at Augusta Rs, WI, averaging 82°F by day and 59°F at night; January is the coldest at 22°F and 4°F. A freezing night is all but certain in every month from October to April (a 90% chance or more). From June to August the chance of a 32°F night stays under 10% each month. In spring, May still brings one in 73% of years.

Warmth for growing adds up to 2,339 growing degree days a year (base 50°F), fewer than at 62% of the 182 Wisconsin stations. 34% of them (787) have built up by the end of June, and July adds the most, 627. Precipitation totals 34.6 inches a year, most in June (5.1") and least in January (1.0"); May to September bring 63% of it.

The nearest other station, Blair, WI, 18 miles south of Osseo, has a last frost 2 days later (May 9), the same first-frost date, a season 3 days shorter.

The first measurable snow (0.1 inch or more) in Osseo usually arrives around November 8, and the last of the season around April 12. Those are the middle dates across the winters of 1991–2020 at Augusta Rs, WI, 9.6 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 25 days after the last snow.

ZIP 54758 is 10 miles from Augusta Rs, WI, which stands at 960 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 2 other ZIP codes share the station; its figures are presented in full for 54742 (Fall Creek). The 2023 USDA Plant Hardiness Zone Map lists ZIP 54758 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.