Frost Dates for 62450 — Olney, Illinois

Half of springs at Olney 2S, IL see their last 32°F night by April 15; only one in ten is past it by April 1, and one in ten still has one after May 3. Planting tender crops after April 22 leaves a 30% risk of a frost on them, after April 26 20%, and after May 3 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 23 in half of years, as early as October 8 one year in ten, and holds off past November 3 one year in ten. A hard freeze of 28°F follows 9 days later, around November 1; in spring the one-in-ten date for 28°F is April 18, 15 days before the 32°F one. The freeze-free season lasts 189 days in a typical year, longer than at 62% of the 158 Illinois stations; it reaches 210 days one year in ten and falls short of 169 one year in ten. On average 105 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 26, and return around October 13. Severe cold of 16°F or below comes every winter, usually between December 2 and March 3.

July is the warmest month at Olney 2S, IL, averaging 87°F by day and 66°F at night; January is the coldest at 38°F and 21°F. A freezing night is all but certain in every month from November to March (a 90% chance or more). From June to September the chance of a 32°F night stays under 10% each month. In spring, April still brings one in 90% of years and May still brings one in 13% of years.

Warmth for growing adds up to 3,829 growing degree days a year (base 50°F), more than at 73% of the 158 Illinois stations. 37% of them (1,402) have built up by the end of June, and July adds the most, 812. Precipitation totals 48.8 inches a year, most in May (5.6") and least in February (2.6"); May to September bring 45% of it.

The nearest other station, Newton, IL, 19 miles north of Olney, has a last frost 2 days earlier (April 13), a first frost 1 day earlier (October 22), a season 1 day longer.

The first measurable snow (0.1 inch or more) in Olney usually arrives around December 10, and the last of the season around February 27. Those are the middle dates across the winters of 1991–2020 at Olney 2S, 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 47 days after the last snow.

ZIP 62450 is 2 miles from Olney 2S, IL, which stands at 459 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 62450 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.