Frost Dates for 62565 — Shelbyville, Illinois

Half of springs at Shelbyville Dam, IL 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 28. Planting tender crops after April 17 leaves a 30% risk of a frost on them, after April 21 20%, and after April 28 10%. The 18 days between the even-odds date and the one-in-ten date is wider than at 92% of the 158 Illinois stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 24 in half of years, as early as October 8 one year in ten, and holds off past November 5 one year in ten. A hard freeze of 28°F follows 10 days later, around November 3; in spring the one-in-ten date for 28°F is April 14, 14 days before the 32°F one. The freeze-free season lasts 195 days in a typical year, longer than at 78% of the 158 Illinois stations; it reaches 214 days one year in ten and falls short of 175 one year in ten. On average 114 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 14. Severe cold of 16°F or below comes every winter, usually between December 5 and March 3.

July is the warmest month at Shelbyville Dam, IL, averaging 86°F by day and 67°F at night; January is the coldest at 36°F and 19°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 86% of years.

Warmth for growing adds up to 3,769 growing degree days a year (base 50°F), more than at 72% of the 158 Illinois stations. 36% of them (1,363) have built up by the end of June, and July adds the most, 815. Precipitation totals 41.6 inches a year, most in May (4.7") and least in February (2.1"); May to September bring 48% of it.

The nearest other station, Sullivan 3S, IL, 15 miles northeast of Shelbyville, has a last frost 5 days later (April 15), a first frost 2 days earlier (October 22), a season 8 days shorter.

The first measurable snow (0.1 inch or more) in Shelbyville usually arrives around December 23, and the last of the season around February 24. Those are the middle dates across the winters of 1991–2020 at Shelbyville Dam, IL, 1.5 miles away: half of years saw snow earlier, half later. Snow fell in 88% of those winters. The last 32°F night of spring typically comes 45 days after the last snow.

ZIP 62565 is 2 miles from Shelbyville Dam, IL, which stands at 650 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 62565 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.