Frost Dates for 62233 — Chester, Illinois

Half of springs at Kaskaskia Rvr Navigation Lock, IL see their last 32°F night by April 8; only one in ten is past it by March 22, and one in ten still has one after April 25. Planting tender crops after April 15 leaves a 30% risk of a frost on them, after April 19 20%, and after April 25 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 30 in half of years, as early as October 15 one year in ten, and holds off past November 13 one year in ten. A hard freeze of 28°F follows 11 days later, around November 10; in spring the one-in-ten date for 28°F is April 13, 12 days before the 32°F one. The freeze-free season lasts 202 days in a typical year, longer than at 90% of the 158 Illinois stations; it reaches 226 days one year in ten and falls short of 180 one year in ten. On average 99 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 20, and return around October 18. Severe cold of 16°F or below comes every winter, usually between December 16 and February 24.

July is the warmest month at Kaskaskia Rvr Navigation Lock, IL, averaging 89°F by day and 68°F at night; January is the coldest at 40°F and 24°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 73% of years.

Warmth for growing adds up to 4,230 growing degree days a year (base 50°F), more than at 93% of the 158 Illinois stations. 37% of them (1,568) have built up by the end of June, and July adds the most, 890. Precipitation totals 42.8 inches a year, most in May (5.2") and least in February (2.4"); May to September bring 46% of it.

The nearest other station, Perryville Wtp, MO, 14 miles south of Chester, has a last frost 11 days later (April 19), a first frost 10 days earlier (October 20), a season 20 days shorter.

The first measurable snow (0.1 inch or more) in Chester usually arrives around December 22, and the last of the season around February 24. Those are the middle dates across the winters of 1991–2020 at Chester, IL, 1.4 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 43 days after the last snow.

ZIP 62233 is 8 miles from Kaskaskia Rvr Navigation Lock, IL, which stands at 380 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 63670 (Ste Genevieve). The 2023 USDA Plant Hardiness Zone Map lists ZIP 62233 in zone 7a, the band where the coldest night of the year averaged 0 to 5°F (-17.8 to -15.0°C) over 1991–2020; a zone describes winter lows, not frost dates.