Frost Dates for 53036 — Ixonia, Wisconsin

Half of springs at Oconomowoc Wwtp, WI see their last 32°F night by April 30; only one in ten is past it by April 16, and one in ten still has one after May 17. Planting tender crops after May 6 leaves a 30% risk of a frost on them, after May 10 20%, and after May 17 10%. The 17 days between the even-odds date and the one-in-ten date is wider than at 90% of the 182 Wisconsin stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 12 in half of years, as early as September 29 one year in ten, and holds off past October 27 one year in ten. A hard freeze of 28°F follows 12 days later, around October 24; in spring the one-in-ten date for 28°F is May 3, 14 days before the 32°F one. The freeze-free season lasts 164 days in a typical year, longer than at 71% of the 182 Wisconsin stations; it reaches 185 days one year in ten and falls short of 143 one year in ten. On average 146 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 12 days longer, to about May 12, and return around October 2. Severe cold of 16°F or below comes every winter, usually between November 22 and March 18.

July is the warmest month at Oconomowoc Wwtp, WI, averaging 82°F by day and 61°F at night; January is the coldest at 28°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 47% of years.

Warmth for growing adds up to 2,708 growing degree days a year (base 50°F), more than at 84% of the 182 Wisconsin stations. 33% of them (884) have built up by the end of June, and July adds the most, 674. Precipitation totals 36.9 inches a year, most in June (4.9") and least in February (1.6"); May to September bring 56% of it.

The nearest other station, Watertown Wwtp, WI, 8 miles west of Ixonia, has a last frost 2 days earlier (April 28), the same first-frost date, a season 3 days longer.

The first measurable snow (0.1 inch or more) in Ixonia usually arrives around November 21, and the last of the season around April 10. Those are the middle dates across the winters of 1991–2020 at Oconomowoc Wwtp, WI, 6.5 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 20 days after the last snow.

ZIP 53036 is 7 miles from Oconomowoc Wwtp, WI, which stands at 858 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 53066 (Oconomowoc). The 2023 USDA Plant Hardiness Zone Map lists ZIP 53036 in zone 5a, the band where the coldest night of the year averaged -20 to -15°F (-28.9 to -26.1°C) over 1991–2020; a zone describes winter lows, not frost dates.