Frost Dates for 60436 — Joliet, Illinois

Half of springs at Joliet Brandon Rd Dam, IL see their last 32°F night by April 19; only one in ten is past it by April 3, and one in ten still has one after May 7. Planting tender crops after April 26 leaves a 30% risk of a frost on them, after April 30 20%, and after May 7 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 25 in half of years, as early as October 12 one year in ten, and holds off past November 6 one year in ten. A hard freeze of 28°F follows 10 days later, around November 4; in spring the one-in-ten date for 28°F is April 21, 16 days before the 32°F one. The freeze-free season lasts 188 days in a typical year, longer than at 58% of the 158 Illinois stations; it reaches 208 days one year in ten and falls short of 167 one year in ten. On average 126 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 1, and return around October 15. Severe cold of 16°F or below comes every winter, usually between December 3 and March 7.

July is the warmest month at Joliet Brandon Rd Dam, IL, averaging 84°F by day and 64°F at night; January is the coldest at 31°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 20% of years.

Warmth for growing adds up to 3,179 growing degree days a year (base 50°F), fewer than at 73% of the 158 Illinois stations. 34% of them (1,066) have built up by the end of June, and July adds the most, 739. Precipitation totals 38.1 inches a year, most in July (4.6") and least in February (1.8"); May to September bring 54% of it.

The nearest other station, Romeoville WFO, IL, 7 miles north of Joliet, has a last frost 1 day later (April 20), a first frost 3 days earlier (October 22), a season 4 days shorter.

The first measurable snow (0.1 inch or more) in Joliet usually arrives around December 5, and the last of the season around March 9. Those are the middle dates across the winters of 1991–2020 at Joliet Brandon Rd Dam, IL, 0.3 miles away: half of years saw snow earlier, half later. Snow fell in 93% of those winters. The last 32°F night of spring typically comes 41 days after the last snow.

ZIP 60436 is under a mile from Joliet Brandon Rd Dam, IL, which stands at 543 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 9 other ZIP codes share the station; its figures are presented in full for 60435 (Joliet). The 2023 USDA Plant Hardiness Zone Map lists ZIP 60436 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.