Frost Dates for 61880 — Tolono, Illinois

Half of springs at Champaign Willard Airport, IL see their last 32°F night by April 19; only one in ten is past it by April 6, and one in ten still has one after May 5. Planting tender crops after April 26 leaves a 30% risk of a frost on them, after April 30 20%, and after May 5 10%. The 16 days between the even-odds date and the one-in-ten date is narrower than at 22% of the 158 Illinois stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 17 in half of years, as early as October 3 one year in ten, and holds off past October 31 one year in ten. A hard freeze of 28°F follows 11 days later, around October 28; in spring the one-in-ten date for 28°F is April 24, 11 days before the 32°F one. The freeze-free season lasts 180 days in a typical year, shorter than at 60% of the 158 Illinois stations; it reaches 199 days one year in ten and falls short of 159 one year in ten. On average 122 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 30, and return around October 8. Severe cold of 16°F or below comes every winter, usually between November 29 and March 9.

July is the warmest month at Champaign Willard Airport, IL, averaging 85°F by day and 64°F at night; January is the coldest at 34°F and 18°F. A freezing night is all but certain in every month from October to April (a 90% chance or more). From June to September the chance of a 32°F night stays under 10% each month. In spring, May still brings one in 18% of years.

Warmth for growing adds up to 3,574 growing degree days a year (base 50°F), more than at 57% of the 158 Illinois stations. 37% of them (1,336) have built up by the end of June, and July adds the most, 766. Precipitation totals 37.1 inches a year, most in May (4.4") and least in February (1.8"); May to September bring 51% of it.

The nearest other station, Champaign 3S, IL, 7 miles north of Tolono, has a last frost 4 days earlier (April 15), a first frost 7 days later (October 24), a season 10 days longer.

The first measurable snow (0.1 inch or more) in Tolono usually arrives around December 1, and the last of the season around March 12. Those are the middle dates across the winters of 1991–2020 at Philo, IL, 5.6 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 38 days after the last snow.

ZIP 61880 is 4 miles from Champaign Willard Airport, IL, which stands at 754 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 61880 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.