Frost Dates for 62501 — Oakley, Illinois

Half of springs at Decatur Airport, IL see their last 32°F night by April 16; only one in ten is past it by April 3, and one in ten still has one after April 30. Planting tender crops after April 22 leaves a 30% risk of a frost on them, after April 25 20%, and after April 30 10%. The 14 days between the even-odds date and the one-in-ten date is narrower than at 82% 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 3 one year in ten. A hard freeze of 28°F follows 11 days later, around November 2; in spring the one-in-ten date for 28°F is April 21, 9 days before the 32°F one. The freeze-free season lasts 187 days in a typical year, longer than at 54% of the 158 Illinois stations; it reaches 206 days one year in ten and falls short of 167 one year in ten. On average 113 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 10 days longer, to about April 26, and return around October 11. Severe cold of 16°F or below comes every winter, usually between December 5 and March 5.

July is the warmest month at Decatur Airport, IL, averaging 86°F by day and 66°F at night; January is the coldest at 35°F and 20°F. A freezing night is all but certain in every month from November to April (a 90% chance or more). From May to September the chance of a 32°F night stays under 10% each month.

Warmth for growing adds up to 3,646 growing degree days a year (base 50°F), more than at 62% of the 158 Illinois stations. 37% of them (1,345) have built up by the end of June, and July adds the most, 797. Precipitation totals 36.4 inches a year, most in May (4.4") and least in February (1.8"); May to September bring 50% of it.

The nearest other station, Decatur Wtp, IL, 13 miles southwest of Oakley, has a last frost 2 days earlier (April 14), a first frost 2 days later (October 24), a season 5 days longer.

The first measurable snow (0.1 inch or more) in Oakley usually arrives around December 2, and the last of the season around March 11. Those are the middle dates across the winters of 1991–2020 at Cisco, IL, 5 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 36 days after the last snow.

ZIP 62501 is 11 miles from Decatur Airport, IL, which stands at 675 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 62549 (Mt Zion). The 2023 USDA Plant Hardiness Zone Map lists ZIP 62501 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.