Frost Dates for 53818 — Platteville, Wisconsin

Half of springs at Platteville, WI see their last 32°F night by April 30; only one in ten is past it by April 14, and one in ten still has one after May 13. Planting tender crops after May 4 leaves a 30% risk of a frost on them, after May 8 20%, and after May 13 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 13 in half of years, as early as September 29 one year in ten, and holds off past October 24 one year in ten. A hard freeze of 28°F follows 9 days later, around October 22; in spring the one-in-ten date for 28°F is May 2, 11 days before the 32°F one. The freeze-free season lasts 166 days in a typical year, longer than at 76% of the 182 Wisconsin stations; it reaches 185 days one year in ten and falls short of 146 one year in ten. On average 154 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 8 days longer, to about May 8, and return around October 3. Severe cold of 16°F or below comes every winter, usually between November 22 and March 18.

July is the warmest month at Platteville, WI, averaging 82°F by day and 62°F at night; January is the coldest at 26°F and 10°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 44% of years.

Warmth for growing adds up to 2,688 growing degree days a year (base 50°F), more than at 81% of the 182 Wisconsin stations. 33% of them (895) have built up by the end of June, and July adds the most, 676. Precipitation totals 40.2 inches a year, most in June (6.0") and least in January (1.2"); May to September bring 61% of it.

The nearest other station, Dubuque L&D 11, IA, 16 miles southwest of Platteville and 370 feet lower, has a last frost 11 days earlier (April 19), a first frost 8 days later (October 21), a season 18 days longer.

The first measurable snow (0.1 inch or more) in Platteville usually arrives around November 21, and the last of the season around March 29. Those are the middle dates across the winters of 1991–2020 at Platteville, WI, 1.1 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 32 days after the last snow.

ZIP 53818 is 1 mile from Platteville, WI, which stands at 990 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 53818 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.