Frost Dates for 62237 — Coulterville, Illinois

Half of springs at Sparta 1 W, IL see their last 32°F night by April 12; only one in ten is past it by March 29, and one in ten still has one after April 29. Planting tender crops after April 19 leaves a 30% risk of a frost on them, after April 23 20%, and after April 29 10%. The 17 days between the even-odds date and the one-in-ten date is wider than at 79% of the 158 Illinois stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 22 in half of years, as early as October 7 one year in ten, and holds off past November 2 one year in ten. A hard freeze of 28°F follows 10 days later, around November 1; in spring the one-in-ten date for 28°F is April 16, 13 days before the 32°F one. The freeze-free season lasts 191 days in a typical year, longer than at 72% of the 158 Illinois stations; it reaches 210 days one year in ten and falls short of 168 one year in ten. On average 109 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 24, and return around October 12. Severe cold of 16°F or below comes every winter, usually between December 7 and March 2.

July is the warmest month at Sparta 1 W, IL, averaging 88°F by day and 66°F at night; January is the coldest at 40°F and 22°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 84% of years.

Warmth for growing adds up to 3,944 growing degree days a year (base 50°F), more than at 82% of the 158 Illinois stations. 37% of them (1,462) have built up by the end of June, and July adds the most, 826. Precipitation totals 45.7 inches a year, most in April (5.2") and least in February (2.6"); May to September bring 45% of it.

The nearest other station, Nashville 1 E, IL, 17 miles northeast of Coulterville, has a last frost 5 days earlier (April 7), a first frost 4 days later (October 26), a season 10 days longer.

The first measurable snow (0.1 inch or more) in Coulterville usually arrives around December 15, and the last of the season around March 1. Those are the middle dates across the winters of 1991–2020 at Sparta 1 W, IL, 8.1 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 42 days after the last snow.

ZIP 62237 is 8 miles from Sparta 1 W, IL, which stands at 535 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 2 other ZIP codes share the station; its figures are presented in full for 62286 (Sparta). The 2023 USDA Plant Hardiness Zone Map lists ZIP 62237 in zone 6b, the band where the coldest night of the year averaged -5 to 0°F (-20.6 to -17.8°C) over 1991–2020; a zone describes winter lows, not frost dates.