Frost Dates for 50849 — Greenfield, Iowa

Half of springs at Greenfield, IA see their last 32°F night by April 25; only one in ten is past it by April 12, and one in ten still has one after May 7. Planting tender crops after May 1 leaves a 30% risk of a frost on them, after May 3 20%, and after May 7 10%. The 12 days between the even-odds date and the one-in-ten date is narrower than at 67% 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 26 one year in ten, and holds off past October 26 one year in ten. A hard freeze of 28°F follows 11 days later, around October 23; in spring the one-in-ten date for 28°F is April 29, 8 days before the 32°F one. The freeze-free season lasts 170 days in a typical year, longer than at 69% of the 132 Iowa stations; it reaches 189 days one year in ten and falls short of 149 one year in ten. On average 138 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 4, and return around October 2. Severe cold of 16°F or below comes every winter, usually between November 15 and March 19.

July is the warmest month at Greenfield, IA, averaging 84°F by day and 64°F at night; January is the coldest at 30°F and 11°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 31% of years.

Warmth for growing adds up to 3,164 growing degree days a year (base 50°F), more than at 69% of the 132 Iowa stations. 34% of them (1,088) have built up by the end of June, and July adds the most, 752. Precipitation totals 36.8 inches a year, most in May (5.3") and least in January (0.9"); May to September bring 61% of it.

The nearest other station, Creston 2 SW, IA, 19 miles south of Greenfield, has a last frost 3 days later (April 28), a first frost 1 day earlier (October 11), a season 6 days shorter.

The first measurable snow (0.1 inch or more) in Greenfield usually arrives around November 22, and the last of the season around March 20. Those are the middle dates across the winters of 1991–2020 at Greenfield, IA, 1.5 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 36 days after the last snow.

ZIP 50849 is 2 miles from Greenfield, IA, which stands at 1,316 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 50849 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.