Frost Dates for 61012 — Capron, Illinois

Half of springs at Marengo, IL see their last 32°F night by April 28; only one in ten is past it by April 15, and one in ten still has one after May 14. Planting tender crops after May 4 leaves a 30% risk of a frost on them, after May 9 20%, and after May 14 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 12 in half of years, as early as September 28 one year in ten, and holds off past October 27 one year in ten. A hard freeze of 28°F follows 13 days later, around October 25; in spring the one-in-ten date for 28°F is May 4, 10 days before the 32°F one. The freeze-free season lasts 166 days in a typical year, shorter than at 92% of the 158 Illinois stations; it reaches 187 days one year in ten and falls short of 146 one year in ten. On average 147 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 May 10, and return around October 3. Severe cold of 16°F or below comes every winter, usually between November 24 and March 16.

July is the warmest month at Marengo, IL, averaging 84°F by day and 62°F at night; January is the coldest at 29°F and 13°F. A freezing night is all but certain in every month from October to April (a 90% chance or more). From June to August the chance of a 32°F night stays under 10% each month. In spring, May still brings one in 42% of years.

Warmth for growing adds up to 2,850 growing degree days a year (base 50°F), fewer than at 91% of the 158 Illinois stations. 33% of them (947) have built up by the end of June, and July adds the most, 700. Precipitation totals 37.7 inches a year, most in May (4.6") and least in February (1.6"); May to September bring 56% of it.

The nearest other station, Clinton Wwtp, WI, 12 miles northwest of Capron, has a last frost 2 days later (April 30), a first frost 2 days earlier (October 10), a season 5 days shorter.

The first measurable snow (0.1 inch or more) in Capron usually arrives around November 22, and the last of the season around March 31. Those are the middle dates across the winters of 1991–2020 at Harvard, IL, 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 28 days after the last snow.

ZIP 61012 is 12 miles from Marengo, IL, which stands at 815 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 5 other ZIP codes share the station; its figures are presented in full for 61008 (Belvidere). The 2023 USDA Plant Hardiness Zone Map lists ZIP 61012 in zone 5b, the band where the coldest night of the year averaged -15 to -10°F (-26.1 to -23.3°C) over 1991–2020; a zone describes winter lows, not frost dates.