Frost Dates for 52556 — Fairfield, Iowa

Half of springs at Fairfield, IA see their last 32°F night by April 27; only one in ten is past it by April 13, and one in ten still has one after May 14. Planting tender crops after May 3 leaves a 30% risk of a frost on them, after May 8 20%, and after May 14 10%. The 17 days between the even-odds date and the one-in-ten date is wider than at 98% of the 132 Iowa stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 12 in half of years, as early as September 27 one year in ten, and holds off past October 25 one year in ten. A hard freeze of 28°F follows 10 days later, around October 22; in spring the one-in-ten date for 28°F is May 1, 13 days before the 32°F one. The freeze-free season lasts 168 days in a typical year, longer than at 62% of the 132 Iowa stations; it reaches 188 days one year in ten and falls short of 145 one year in ten. On average 127 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 May 8, and return around October 3. Severe cold of 16°F or below comes every winter, usually between November 18 and March 15.

July is the warmest month at Fairfield, IA, averaging 84°F by day and 64°F at night; January is the coldest at 31°F and 14°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 39% of years.

Warmth for growing adds up to 3,143 growing degree days a year (base 50°F), more than at 67% of the 132 Iowa stations. 35% of them (1,101) have built up by the end of June, and July adds the most, 739. Precipitation totals 38.4 inches a year, most in May (5.5") and least in January (1.5"); May to September bring 57% of it.

The nearest other station, Mt Pleasant 1 SSW, IA, 21 miles east of Fairfield, has a last frost 3 days later (April 30), a first frost 2 days earlier (October 10), a season 5 days shorter.

The first measurable snow (0.1 inch or more) in Fairfield usually arrives around December 1, and the last of the season around March 16. Those are the middle dates across the winters of 1991–2020 at Fairfield, IA, 0.4 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 42 days after the last snow.

ZIP 52556 is under a mile from Fairfield, IA, which stands at 740 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 52556 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.