Frost Dates for 50049 — Chariton, Iowa

Half of springs at Chariton 1 E, IA see their last 32°F night by May 5; only one in ten is past it by April 21, and one in ten still has one after May 19. Planting tender crops after May 10 leaves a 30% risk of a frost on them, after May 14 20%, and after May 19 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 5 in half of years, as early as September 20 one year in ten, and holds off past October 18 one year in ten. A hard freeze of 28°F follows 11 days later, around October 16; in spring the one-in-ten date for 28°F is May 10, 9 days before the 32°F one. The freeze-free season lasts 151 days in a typical year, shorter than at 94% of the 132 Iowa stations; it reaches 169 days one year in ten and falls short of 130 one year in ten. On average 154 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 16, and return around September 26. Severe cold of 16°F or below comes every winter, usually between November 13 and March 26.

July is the warmest month at Chariton 1 E, IA, averaging 85°F by day and 62°F at night; January is the coldest at 31°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 68% of years.

Warmth for growing adds up to 2,887 growing degree days a year (base 50°F), fewer than at 64% of the 132 Iowa stations. 34% of them (969) have built up by the end of June, and July adds the most, 713. Precipitation totals 37.4 inches a year, most in May (5.4") and least in January (1.0"); May to September bring 60% of it.

The nearest other station, Allerton, IA, 23 miles south of Chariton, has a last frost 14 days earlier (April 21), a first frost 14 days later (October 19), a season 27 days longer.

The first measurable snow (0.1 inch or more) in Chariton usually arrives around November 30, and the last of the season around March 16. Those are the middle dates across the winters of 1991–2020 at Chariton 1 E, IA, 1.3 miles away: half of years saw snow earlier, half later. Snow fell in 96% of those winters. The last 32°F night of spring typically comes 50 days after the last snow.

ZIP 50049 is 1 mile from Chariton 1 E, IA, which stands at 965 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 50049 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.