Frost Dates for 50144 — Leon, Iowa

Half of springs at Leon 6 ESE, IA see their last 32°F night by April 30; only one in ten is past it by April 16, and one in ten still has one after May 15. Planting tender crops after May 6 leaves a 30% risk of a frost on them, after May 11 20%, and after May 15 10%. The 15 days between the even-odds date and the one-in-ten date is wider than at 82% of the 132 Iowa stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 8 in half of years, as early as September 26 one year in ten, and holds off past October 22 one year in ten. A hard freeze of 28°F follows 11 days later, around October 19; in spring the one-in-ten date for 28°F is May 4, 11 days before the 32°F one. The freeze-free season lasts 161 days in a typical year, shorter than at 67% of the 132 Iowa stations; it reaches 182 days one year in ten and falls short of 141 one year in ten. On average 150 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 9, and return around September 29. Severe cold of 16°F or below comes every winter, usually between November 18 and March 17.

July is the warmest month at Leon 6 ESE, IA, averaging 86°F by day and 63°F at night; January is the coldest at 33°F and 13°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 49% of years.

Warmth for growing adds up to 3,078 growing degree days a year (base 50°F), more than at 60% of the 132 Iowa stations. 35% of them (1,071) have built up by the end of June, and July adds the most, 749. Precipitation totals 39.4 inches a year, most in June (5.6") and least in January (0.9"); May to September bring 61% of it.

The nearest other station, Lamoni, IA, 13 miles southwest of Leon, has a last frost 13 days earlier (April 17), a first frost 13 days later (October 21), a season 23 days longer.

The first measurable snow (0.1 inch or more) in Leon usually arrives around November 29, and the last of the season around March 22. Those are the middle dates across the winters of 1991–2020 at Leon 6 ESE, IA, 5.2 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 39 days after the last snow.

ZIP 50144 is 5 miles from Leon 6 ESE, IA, which stands at 1,000 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 50144 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.