Frost Dates for 60175 — St Charles, Illinois

Half of springs at West Chicago Dupage Airport, IL see their last 32°F night by April 25; only one in ten is past it by April 11, and one in ten still has one after May 12. Planting tender crops after May 1 leaves a 30% risk of a frost on them, after May 5 20%, and after May 12 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 19 in half of years, as early as October 5 one year in ten, and holds off past October 30 one year in ten. A hard freeze of 28°F follows 10 days later, around October 29; in spring the one-in-ten date for 28°F is April 29, 13 days before the 32°F one. The freeze-free season lasts 174 days in a typical year, shorter than at 76% of the 158 Illinois stations; it reaches 194 days one year in ten and falls short of 153 one year in ten. On average 134 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 May 6, and return around October 7. Severe cold of 16°F or below comes every winter, usually between November 30 and March 12.

July is the warmest month at West Chicago Dupage Airport, IL, averaging 84°F by day and 63°F at night; January is the coldest at 31°F and 16°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 32% of years.

Warmth for growing adds up to 3,059 growing degree days a year (base 50°F), fewer than at 82% of the 158 Illinois stations. 34% of them (1,033) have built up by the end of June, and July adds the most, 733. Precipitation totals 33.2 inches a year, most in May (4.3") and least in February (1.2"); May to September bring 55% of it.

The nearest other station, Elgin, IL, 10 miles northeast of St Charles, has a last frost 1 day later (April 26), a first frost 1 day earlier (October 18).

The first measurable snow (0.1 inch or more) in St Charles usually arrives around December 4, and the last of the season around March 21. Those are the middle dates across the winters of 1991–2020 at Elburn, IL, 6.7 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 35 days after the last snow.

ZIP 60175 is 7 miles from West Chicago Dupage Airport, IL, which stands at 754 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 6 other ZIP codes share the station; its figures are presented in full for 60188 (Carol Stream). The 2023 USDA Plant Hardiness Zone Map lists ZIP 60175 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.