Frost Dates for 54126 — Greenleaf, Wisconsin

Half of springs at Brillion, WI see their last 32°F night by May 6; only one in ten is past it by April 22, and one in ten still has one after May 21. Planting tender crops after May 12 leaves a 30% risk of a frost on them, after May 16 20%, and after May 21 10%. The 15 days between the even-odds date and the one-in-ten date is narrower than at 30% of the 182 Wisconsin stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 6 in half of years, as early as September 23 one year in ten, and holds off past October 21 one year in ten. A hard freeze of 28°F follows 12 days later, around October 18; in spring the one-in-ten date for 28°F is May 12, 9 days before the 32°F one. The freeze-free season lasts 151 days in a typical year, shorter than at 62% of the 182 Wisconsin stations; it reaches 173 days one year in ten and falls short of 131 one year in ten. On average 159 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 11 days longer, to about May 17, and return around September 26. Severe cold of 16°F or below comes every winter, usually between November 23 and March 24.

July is the warmest month at Brillion, WI, averaging 82°F by day and 59°F at night; January is the coldest at 26°F and 10°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 67% of years.

Warmth for growing adds up to 2,374 growing degree days a year (base 50°F), fewer than at 58% of the 182 Wisconsin stations. 32% of them (771) have built up by the end of June, and July adds the most, 631. Precipitation totals 32.2 inches a year, most in June (4.5") and least in February (1.0"); May to September bring 57% of it.

The nearest other station, Denmark Wwtp, WI, 12 miles east of Greenleaf, has the same 50% last-frost date, a first frost 6 days later (October 12), a season 7 days longer.

The first measurable snow (0.1 inch or more) in Greenleaf usually arrives around November 22, and the last of the season around April 6. Those are the middle dates across the winters of 1991–2020 at Brillion, WI, 9.1 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 30 days after the last snow.

ZIP 54126 is 9 miles from Brillion, WI, which stands at 810 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 5 other ZIP codes share the station; its figures are presented in full for 54110 (Brillion). The 2023 USDA Plant Hardiness Zone Map lists ZIP 54126 in zone 5b, the band where the coldest night of the year averaged -15 to -10°F (-26.1 to -23.3°C) over 1991–2020; a zone describes winter lows, not frost dates.