Frost Dates for 62206 — Cahokia, Illinois

Half of springs at Cahokia St Louis Airport, IL see their last 32°F night by April 8; only one in ten is past it by March 23, and one in ten still has one after April 23. Planting tender crops after April 14 leaves a 30% risk of a frost on them, after April 18 20%, and after April 23 10%. The 15 days between the even-odds date and the one-in-ten date is narrower than at 54% of the 158 Illinois stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 26 in half of years, as early as October 12 one year in ten, and holds off past November 7 one year in ten. A hard freeze of 28°F follows 11 days later, around November 6; in spring the one-in-ten date for 28°F is April 12, 11 days before the 32°F one. The freeze-free season lasts 200 days in a typical year, longer than at 87% of the 158 Illinois stations; it reaches 221 days one year in ten and falls short of 180 one year in ten. On average 98 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 April 19, and return around October 17. Severe cold of 16°F or below comes every winter, usually between December 14 and February 24.

July is the warmest month at Cahokia St Louis Airport, IL, averaging 89°F by day and 69°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 72% of years.

Warmth for growing adds up to 4,263 growing degree days a year (base 50°F), more than at 95% of the 158 Illinois stations. 38% of them (1,615) have built up by the end of June, and July adds the most, 896. Precipitation totals 41.0 inches a year, most in May (4.8") and least in February (2.0"); May to September bring 49% of it.

The nearest other station, Cahokia, IL, 2 miles west of Cahokia, has a last frost 2 days earlier (April 6), a first frost 1 day later (October 27), a season 3 days longer.

The first measurable snow (0.1 inch or more) in Cahokia usually arrives around December 12, and the last of the season around March 14. Those are the middle dates across the winters of 1991–2020 at Cahokia, IL, 1.7 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 25 days after the last snow.

ZIP 62206 is under a mile from Cahokia St Louis Airport, IL, which stands at 413 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 10 other ZIP codes share the station; its figures are presented in full for 62234 (Collinsville). The 2023 USDA Plant Hardiness Zone Map lists ZIP 62206 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.