Frost Dates for 52627 — Fort Madison, Iowa

Half of springs at Fort Madison, IA see their last 32°F night by April 12; only one in ten is past it by April 1, and one in ten still has one after April 26. Planting tender crops after April 18 leaves a 30% risk of a frost on them, after April 22 20%, and after April 26 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 25 in half of years, as early as October 11 one year in ten, and holds off past November 6 one year in ten. A hard freeze of 28°F follows 10 days later, around November 4; in spring the one-in-ten date for 28°F is April 17, 9 days before the 32°F one. The freeze-free season lasts 194 days in a typical year, longer than at 98% of the 132 Iowa stations; it reaches 212 days one year in ten and falls short of 174 one year in ten. On average 110 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 April 24, and return around October 16. Severe cold of 16°F or below comes every winter, usually between December 1 and March 7.

July is the warmest month at Fort Madison, IA, averaging 85°F by day and 68°F at night; January is the coldest at 33°F and 17°F. A freezing night is all but certain in every month from November to March (a 90% chance or more). From May to September the chance of a 32°F night stays under 10% each month. In spring, April still brings one in 90% of years.

Warmth for growing adds up to 3,602 growing degree days a year (base 50°F), more than at 98% of the 132 Iowa stations. 35% of them (1,269) have built up by the end of June, and July adds the most, 815. Precipitation totals 39.4 inches a year, most in June (5.2") and least in January (1.7"); May to September bring 55% of it.

The nearest other station, Donnellson, IA, 12 miles west of Fort Madison and 175 feet higher, has a last frost 5 days later (April 17), a first frost 3 days earlier (October 22), a season 7 days shorter.

The first measurable snow (0.1 inch or more) in Fort Madison usually arrives around December 3, and the last of the season around March 16. Those are the middle dates across the winters of 1991–2020 at Fort Madison, IA, 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 27 days after the last snow.

ZIP 52627 is 1 mile from Fort Madison, IA, which stands at 530 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 52627 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.