Frost Dates for 54656 — Sparta, Wisconsin

Half of springs at Sparta, WI see their last 32°F night by May 9; only one in ten is past it by April 26, and one in ten still has one after May 22. Planting tender crops after May 15 leaves a 30% risk of a frost on them, after May 18 20%, and after May 22 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 18 one year in ten, and holds off past October 13 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 13, 9 days before the 32°F one. The freeze-free season lasts 144 days in a typical year, shorter than at 76% of the 182 Wisconsin stations; it reaches 162 days one year in ten and falls short of 127 one year in ten. On average 165 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 19, and return around September 23. Severe cold of 16°F or below comes every winter, usually between November 11 and March 30.

July is the warmest month at Sparta, WI, averaging 82°F by day and 59°F at night; January is the coldest at 25°F and 6°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 80% of years.

Warmth for growing adds up to 2,443 growing degree days a year (base 50°F), more than at 52% of the 182 Wisconsin stations. 33% of them (816) have built up by the end of June, and July adds the most, 643. Precipitation totals 35.6 inches a year, most in June (5.3") and least in January (1.1"); May to September bring 62% of it.

The nearest other station, Cashton, WI, 16 miles south of Sparta and 588 feet higher, has a last frost 12 days earlier (April 27), a first frost 13 days later (October 14), a season 26 days longer.

The first measurable snow (0.1 inch or more) in Sparta usually arrives around November 26, and the last of the season around April 10. Those are the middle dates across the winters of 1991–2020 at Sparta, WI, 2.3 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 29 days after the last snow.

ZIP 54656 is 2 miles from Sparta, WI, which stands at 782 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 1 other ZIP code shares the station. The 2023 USDA Plant Hardiness Zone Map lists ZIP 54656 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.