Frost Dates for 53191 — Williams Bay, Wisconsin

Half of springs at Lake Geneva Wwtp, WI see their last 32°F night by April 25; only one in ten is past it by April 10, and one in ten still has one after May 10. Planting tender crops after April 30 leaves a 30% risk of a frost on them, after May 4 20%, and after May 10 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 21 in half of years, as early as October 5 one year in ten, and holds off past November 3 one year in ten. A hard freeze of 28°F follows 11 days later, around November 1; in spring the one-in-ten date for 28°F is April 28, 12 days before the 32°F one. The freeze-free season lasts 179 days in a typical year, longer than at 95% of the 182 Wisconsin stations; it reaches 198 days one year in ten and falls short of 156 one year in ten. On average 136 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 5, and return around October 9. Severe cold of 16°F or below comes every winter, usually between November 29 and March 14.

July is the warmest month at Lake Geneva Wwtp, WI, averaging 86°F by day and 63°F at night; January is the coldest at 30°F and 15°F. A freezing night is all but certain in every month from November to April (a 90% chance or more). From June to September the chance of a 32°F night stays under 10% each month. In spring, May still brings one in 29% of years.

Warmth for growing adds up to 3,091 growing degree days a year (base 50°F), more than at 99% of the 182 Wisconsin stations. 33% of them (1,009) have built up by the end of June, and July adds the most, 753. Precipitation totals 37.0 inches a year, most in June (4.8") and least in January (1.9"); May to September bring 53% of it.

The nearest other station, Delavan Wwtp, WI, 8 miles northwest of Williams Bay, has a last frost 3 days later (April 28), a first frost 7 days earlier (October 14), a season 11 days shorter.

The first measurable snow (0.1 inch or more) in Williams Bay usually arrives around November 9, and the last of the season around April 12. Those are the middle dates across the winters of 1991–2020 at Lake Geneva Wwtp, WI, 6.1 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 13 days after the last snow.

ZIP 53191 is 6 miles from Lake Geneva Wwtp, WI, which stands at 846 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 1 other ZIP code shares the station; its figures are presented in full for 53147 (Lake Geneva). The 2023 USDA Plant Hardiness Zone Map lists ZIP 53191 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.