Frost Dates for 50213 — Osceola, Iowa

Half of springs at Osceola, IA see their last 32°F night by April 29; only one in ten is past it by April 13, and one in ten still has one after May 11. Planting tender crops after May 3 leaves a 30% risk of a frost on them, after May 7 20%, and after May 11 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 9 in half of years, as early as September 24 one year in ten, and holds off past October 24 one year in ten. A hard freeze of 28°F follows 11 days later, around October 20; in spring the one-in-ten date for 28°F is May 2, 9 days before the 32°F one. The freeze-free season lasts 162 days in a typical year, shorter than at 61% of the 132 Iowa stations; it reaches 183 days one year in ten and falls short of 142 one year in ten. On average 149 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 8 days longer, to about May 7, and return around September 29. Severe cold of 16°F or below comes every winter, usually between November 16 and March 17.

July is the warmest month at Osceola, IA, averaging 87°F by day and 64°F at night; January is the coldest at 32°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 42% of years.

Warmth for growing adds up to 3,233 growing degree days a year (base 50°F), more than at 76% of the 132 Iowa stations. 34% of them (1,114) have built up by the end of June, and July adds the most, 781. Precipitation totals 38.8 inches a year, most in May (5.5") and least in January (1.0"); May to September bring 61% of it.

The nearest other station, Leon 6 ESE, IA, 22 miles south of Osceola, has a last frost 1 day later (April 30), a first frost 1 day earlier (October 8), a season 1 day shorter.

The first measurable snow (0.1 inch or more) in Osceola usually arrives around December 3, and the last of the season around March 17. Those are the middle dates across the winters of 1991–2020 at Osceola, IA, 1.3 miles away: half of years saw snow earlier, half later. Snow fell in 97% of those winters. The last 32°F night of spring typically comes 43 days after the last snow.

ZIP 50213 is 1 mile from Osceola, IA, which stands at 1,028 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 50213 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.