Frost Dates for 53156 — Palmyra, Wisconsin

Half of springs at Sullivan 3SE, WI see their last 32°F night by May 3; only one in ten is past it by April 18, and one in ten still has one after May 21. Planting tender crops after May 10 leaves a 30% risk of a frost on them, after May 15 20%, and after May 21 10%. The 18 days between the even-odds date and the one-in-ten date is wider than at 96% of the 182 Wisconsin stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 9 in half of years, as early as September 25 one year in ten, and holds off past October 25 one year in ten. A hard freeze of 28°F follows 13 days later, around October 22; in spring the one-in-ten date for 28°F is May 7, 14 days before the 32°F one. The freeze-free season lasts 157 days in a typical year, longer than at 53% of the 182 Wisconsin stations; it reaches 179 days one year in ten and falls short of 135 one year in ten. On average 148 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 13 days longer, to about May 16, and return around September 29. Severe cold of 16°F or below comes every winter, usually between November 21 and March 21.

July is the warmest month at Sullivan 3SE, WI, averaging 82°F by day and 60°F at night; January is the coldest at 27°F and 11°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 59% of years.

Warmth for growing adds up to 2,600 growing degree days a year (base 50°F), more than at 72% of the 182 Wisconsin stations. 32% of them (842) have built up by the end of June, and July adds the most, 654. Precipitation totals 37.8 inches a year, most in June (4.9") and least in January (1.7"); May to September bring 55% of it.

The nearest other station, Whitewater, WI, 7 miles west of Palmyra, has a last frost 1 day earlier (May 2), the same first-frost date.

The first measurable snow (0.1 inch or more) in Palmyra usually arrives around November 18, and the last of the season around April 14. Those are the middle dates across the winters of 1991–2020 at Sullivan 3SE, WI, 6.4 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 19 days after the last snow.

ZIP 53156 is 6 miles from Sullivan 3SE, WI, which stands at 933 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 4 other ZIP codes share the station; its figures are presented in full for 53118 (Dousman). The 2023 USDA Plant Hardiness Zone Map lists ZIP 53156 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.