Frost Dates for 62341 — Hamilton, Illinois

Half of springs at Keokuk Lock Dam 19, IA see their last 32°F night by April 10; only one in ten is past it by March 30, and one in ten still has one after April 26. Planting tender crops after April 17 leaves a 30% risk of a frost on them, after April 21 20%, and after April 26 10%. The 16 days between the even-odds date and the one-in-ten date is narrower than at 22% of the 158 Illinois stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 27 in half of years, as early as October 10 one year in ten, and holds off past November 7 one year in ten. A hard freeze of 28°F follows 9 days later, around November 5; in spring the one-in-ten date for 28°F is April 16, 10 days before the 32°F one. The freeze-free season lasts 198 days in a typical year, longer than at 84% of the 158 Illinois stations; it reaches 218 days one year in ten and falls short of 177 one year in ten. On average 117 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 12 days longer, to about April 22, and return around October 17. Severe cold of 16°F or below comes every winter, usually between December 2 and March 6.

July is the warmest month at Keokuk Lock Dam 19, IA, averaging 86°F by day and 67°F at night; January is the coldest at 33°F and 17°F. A freezing night is all but certain in every month from November to March (a 90% chance or more). From May to September the chance of a 32°F night stays under 10% each month. In spring, April still brings one in 87% of years.

Warmth for growing adds up to 3,574 growing degree days a year (base 50°F), more than at 58% of the 158 Illinois stations. 35% of them (1,256) have built up by the end of June, and July adds the most, 809. Precipitation totals 39.8 inches a year, most in May (5.3") and least in January (1.6"); May to September bring 55% of it.

The nearest other station, Bentley, IL, 12 miles east of Hamilton, has a last frost 3 days later (April 13), a first frost 5 days earlier (October 22), a season 7 days shorter.

The first measurable snow (0.1 inch or more) in Hamilton usually arrives around December 17, and the last of the season around March 2. Those are the middle dates across the winters of 1991–2020 at Keokuk Lock Dam 19, IA, 2.3 miles away: half of years saw snow earlier, half later. Snow fell in 89% of those winters. The last 32°F night of spring typically comes 39 days after the last snow.

ZIP 62341 is 2 miles from Keokuk Lock Dam 19, IA, which stands at 527 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 1 other ZIP code shares the station; its figures are presented in full for 52632 (Keokuk). The 2023 USDA Plant Hardiness Zone Map lists ZIP 62341 in zone 6a, the band where the coldest night of the year averaged -10 to -5°F (-23.3 to -20.6°C) over 1991–2020; a zone describes winter lows, not frost dates.