Frost Dates for 53566 — Monroe, Wisconsin

Half of springs at Monroe Wwtp, WI see their last 32°F night by April 27; only one in ten is past it by April 12, and one in ten still has one after May 12. Planting tender crops after May 2 leaves a 30% risk of a frost on them, after May 6 20%, and after May 12 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 14 in half of years, as early as September 29 one year in ten, and holds off past October 29 one year in ten. A hard freeze of 28°F follows 11 days later, around October 25; in spring the one-in-ten date for 28°F is May 1, 11 days before the 32°F one. The freeze-free season lasts 170 days in a typical year, longer than at 84% of the 182 Wisconsin stations; it reaches 189 days one year in ten and falls short of 149 one year in ten. On average 150 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 9 days longer, to about May 6, and return around October 4. Severe cold of 16°F or below comes every winter, usually between November 24 and March 16.

July is the warmest month at Monroe Wwtp, WI, averaging 83°F by day and 63°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 38% of years.

Warmth for growing adds up to 2,802 growing degree days a year (base 50°F), more than at 91% of the 182 Wisconsin stations. 35% of them (973) have built up by the end of June, and July adds the most, 699. Precipitation totals 39.9 inches a year, most in June (6.2") and least in January (1.6"); May to September bring 58% of it.

The nearest other station, Brodhead Wwtp, WI, 13 miles east of Monroe and 211 feet lower, has a last frost 2 days later (April 29), a first frost 2 days earlier (October 12), a season 5 days shorter.

The first measurable snow (0.1 inch or more) in Monroe usually arrives around November 22, and the last of the season around March 31. Those are the middle dates across the winters of 1991–2020 at Monroe Wwtp, WI, 1.4 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 27 days after the last snow.

ZIP 53566 is 1 mile from Monroe Wwtp, WI, which stands at 991 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 3 other ZIP codes share the station. The 2023 USDA Plant Hardiness Zone Map lists ZIP 53566 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.