Frost Dates for 60408 — Braidwood, Illinois

Half of springs at Channahon Dresden Isl Dam, 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 May 3. Planting tender crops after April 22 leaves a 30% risk of a frost on them, after April 27 20%, and after May 3 10%. The 17 days between the even-odds date and the one-in-ten date is wider than at 79% of the 158 Illinois stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 26 in half of years, as early as October 13 one year in ten, and holds off past November 8 one year in ten. A hard freeze of 28°F follows 11 days later, around November 6; in spring the one-in-ten date for 28°F is April 19, 14 days before the 32°F one. The freeze-free season lasts 191 days in a typical year, longer than at 72% of the 158 Illinois stations; it reaches 211 days one year in ten and falls short of 172 one year in ten. On average 127 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 14 days longer, to about April 30, and return around October 15. Severe cold of 16°F or below comes every winter, usually between December 3 and March 5.

July is the warmest month at Channahon Dresden Isl Dam, IL, averaging 85°F by day and 65°F at night; January is the coldest at 32°F and 17°F. A freezing night is all but certain in every month from November 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 14% of years.

Warmth for growing adds up to 3,332 growing degree days a year (base 50°F), fewer than at 62% of the 158 Illinois stations. 34% of them (1,130) have built up by the end of June, and July adds the most, 773. Precipitation totals 37.5 inches a year, most in May (4.6") and least in February (1.7"); May to September bring 54% of it.

The nearest other station, Morris 1 NW, IL, 13 miles northwest of Braidwood, has a last frost 4 days later (April 20), a first frost 3 days earlier (October 23), a season 7 days shorter.

The first measurable snow (0.1 inch or more) in Braidwood usually arrives around December 3, and the last of the season around March 23. Those are the middle dates across the winters of 1991–2020 at Morris 1 NW, IL, 13.3 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 24 days after the last snow.

ZIP 60408 is 10 miles from Channahon Dresden Isl Dam, IL, which stands at 505 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 4 other ZIP codes share the station; its figures are presented in full for 60447 (Minooka). The 2023 USDA Plant Hardiness Zone Map lists ZIP 60408 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.