Frost Dates for 62995 — Vienna, Illinois

Half of springs at Dixon Springs Agric Ctr, IL see their last 32°F night by April 14; only one in ten is past it by March 28, and one in ten still has one after April 30. Planting tender crops after April 20 leaves a 30% risk of a frost on them, after April 24 20%, and after April 30 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 21 in half of years, as early as October 6 one year in ten, and holds off past November 2 one year in ten. A hard freeze of 28°F follows 10 days later, around October 31; in spring the one-in-ten date for 28°F is April 19, 11 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 208 days one year in ten and falls short of 169 one year in ten. On average 80 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 24, and return around October 11. Severe cold of 16°F or below comes every winter, usually between December 3 and February 26.

July is the warmest month at Dixon Springs Agric Ctr, IL, averaging 88°F by day and 67°F at night; January is the coldest at 43°F and 26°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 84% of years.

Warmth for growing adds up to 4,288 growing degree days a year (base 50°F), more than at 96% of the 158 Illinois stations. 38% of them (1,637) have built up by the end of June, and July adds the most, 849. Precipitation totals 50.6 inches a year, most in May (5.2") and least in February (3.6"); May to September bring 42% of it.

The nearest other station, Anna 2 NNE, IL, 20 miles west of Vienna, has a last frost 6 days earlier (April 8), a first frost 8 days later (October 29), a season 14 days longer.

The first measurable snow (0.1 inch or more) in Vienna usually arrives around December 22, and the last of the season around February 10. Those are the middle dates across the winters of 1991–2020 at Grand Chain Dam 53, IL, 17.6 miles away: half of years saw snow earlier, half later. Snow fell in 95% of those winters. The last 32°F night of spring typically comes 63 days after the last snow.

ZIP 62995 is 12 miles from Dixon Springs Agric Ctr, IL, which stands at 527 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 2 other ZIP codes share the station. The 2023 USDA Plant Hardiness Zone Map lists ZIP 62995 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.