Frost Dates for 52625 — Donnellson, Iowa

Half of springs at Donnellson, IA see their last 32°F night by April 17; only one in ten is past it by April 4, and one in ten still has one after May 1. Planting tender crops after April 23 leaves a 30% risk of a frost on them, after April 26 20%, and after May 1 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 22 in half of years, as early as October 10 one year in ten, and holds off past November 4 one year in ten. A hard freeze of 28°F follows 10 days later, around November 1; in spring the one-in-ten date for 28°F is April 21, 10 days before the 32°F one. The freeze-free season lasts 187 days in a typical year, longer than at 93% of the 132 Iowa stations; it reaches 207 days one year in ten and falls short of 167 one year in ten. On average 129 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 11 days longer, to about April 28, and return around October 12. Severe cold of 16°F or below comes every winter, usually between November 28 and March 9.

July is the warmest month at Donnellson, IA, averaging 86°F by day and 65°F at night; January is the coldest at 33°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 11% of years.

Warmth for growing adds up to 3,540 growing degree days a year (base 50°F), more than at 95% of the 132 Iowa stations. 36% of them (1,263) have built up by the end of June, and July adds the most, 801. Precipitation totals 39.3 inches a year, most in May (5.0") and least in January (1.5"); May to September bring 56% of it.

The nearest other station, Fort Madison, IA, 13 miles east of Donnellson and 175 feet lower, has a last frost 5 days earlier (April 12), a first frost 3 days later (October 25), a season 7 days longer.

The first measurable snow (0.1 inch or more) in Donnellson usually arrives around December 1, and the last of the season around March 21. Those are the middle dates across the winters of 1991–2020 at Donnellson, IA, 2.1 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 27 days after the last snow.

ZIP 52625 is 2 miles from Donnellson, IA, which stands at 705 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 63445 (Kahoka). The 2023 USDA Plant Hardiness Zone Map lists ZIP 52625 in zone 6a, the band where the coldest night of the year averaged -10 to -5°F (-23.3 to -20.6°C) over 1991–2020; a zone describes winter lows, not frost dates.