Frost Dates for 52356 — Wellman, Iowa

Half of springs at Williamsburg 1E, IA see their last 32°F night by April 28; only one in ten is past it by April 14, and one in ten still has one after May 12. Planting tender crops after May 3 leaves a 30% risk of a frost on them, after May 7 20%, and after May 12 10%. The 14 days between the even-odds date and the one-in-ten date is wider than at 58% of the 132 Iowa stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 9 in half of years, as early as September 24 one year in ten, and holds off past October 21 one year in ten. A hard freeze of 28°F follows 10 days later, around October 19; in spring the one-in-ten date for 28°F is May 2, 10 days before the 32°F one. The freeze-free season lasts 164 days in a typical year, shorter than at 52% of the 132 Iowa stations; it reaches 181 days one year in ten and falls short of 145 one year in ten. On average 151 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 7, and return around September 30. Severe cold of 16°F or below comes every winter, usually between November 17 and March 18.

July is the warmest month at Williamsburg 1E, IA, averaging 84°F by day and 63°F at night; January is the coldest at 28°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 40% of years.

Warmth for growing adds up to 2,981 growing degree days a year (base 50°F), fewer than at 54% of the 132 Iowa stations. 35% of them (1,044) have built up by the end of June, and July adds the most, 722. Precipitation totals 37.8 inches a year, most in May (4.9") and least in January (1.2"); May to September bring 59% of it.

The nearest other station, Washington, IA, 16 miles southeast of Wellman, has the same 50% last-frost date, a first frost 2 days later (October 11), a season 1 day longer.

The first measurable snow (0.1 inch or more) in Wellman usually arrives around November 22, and the last of the season around March 25. Those are the middle dates across the winters of 1991–2020 at Williamsburg 1E, IA, 14.9 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 34 days after the last snow.

ZIP 52356 is 15 miles from Williamsburg 1E, IA, which stands at 780 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 2 other ZIP codes share the station; its figures are presented in full for 52361 (Williamsburg). The 2023 USDA Plant Hardiness Zone Map lists ZIP 52356 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.