Frost Dates for 61310 — Amboy, Illinois

Half of springs at Dixon 1W, IL see their last 32°F night by April 21; only one in ten is past it by April 7, and one in ten still has one after May 5. Planting tender crops after April 28 leaves a 30% risk of a frost on them, after May 1 20%, and after May 5 10%. The 14 days between the even-odds date and the one-in-ten date is narrower than at 82% 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 4 one year in ten, and holds off past October 30 one year in ten. A hard freeze of 28°F follows 11 days later, around October 30; in spring the one-in-ten date for 28°F is April 26, 9 days before the 32°F one. The freeze-free season lasts 180 days in a typical year, shorter than at 60% of the 158 Illinois stations; it reaches 200 days one year in ten and falls short of 158 one year in ten. On average 138 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 2, and return around October 9. Severe cold of 16°F or below comes every winter, usually between November 26 and March 11.

July is the warmest month at Dixon 1W, IL, averaging 83°F by day and 64°F at night; January is the coldest at 29°F and 14°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 21% of years.

Warmth for growing adds up to 3,126 growing degree days a year (base 50°F), fewer than at 75% of the 158 Illinois stations. 35% of them (1,091) have built up by the end of June, and July adds the most, 728. Precipitation totals 40.6 inches a year, most in June (5.6") and least in February (1.8"); May to September bring 56% of it.

The nearest other station, Walnut, IL, 17 miles southwest of Amboy, has a last frost 3 days later (April 24), a first frost 5 days earlier (October 14), a season 8 days shorter.

The first measurable snow (0.1 inch or more) in Amboy usually arrives around December 2, and the last of the season around March 21. Those are the middle dates across the winters of 1991–2020 at Amboy, IL, 1.1 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 31 days after the last snow.

ZIP 61310 is 12 miles from Dixon 1W, IL, which stands at 660 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 3 other ZIP codes share the station; its figures are presented in full for 61021 (Dixon). The 2023 USDA Plant Hardiness Zone Map lists ZIP 61310 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.