Frost Dates for 60150 — Malta, Illinois

Half of springs at De Kalb, IL see their last 32°F night by April 24; only one in ten is past it by April 9, and one in ten still has one after May 10. Planting tender crops after April 30 leaves a 30% risk of a frost on them, after May 4 20%, and after May 10 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 18 in half of years, as early as October 4 one year in ten, and holds off past October 31 one year in ten. A hard freeze of 28°F follows 10 days later, around October 28; in spring the one-in-ten date for 28°F is April 29, 11 days before the 32°F one. The freeze-free season lasts 177 days in a typical year, shorter than at 72% of the 158 Illinois stations; it reaches 197 days one year in ten and falls short of 155 one year in ten. On average 141 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 10 days longer, to about May 4, and return around October 7. Severe cold of 16°F or below comes every winter, usually between November 26 and March 13.

July is the warmest month at De Kalb, IL, averaging 83°F by day and 63°F at night; January is the coldest at 28°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 September the chance of a 32°F night stays under 10% each month. In spring, May still brings one in 29% of years.

Warmth for growing adds up to 2,987 growing degree days a year (base 50°F), fewer than at 85% of the 158 Illinois stations. 34% of them (1,018) have built up by the end of June, and July adds the most, 719. Precipitation totals 37.3 inches a year, most in May (4.8") and least in January (1.7"); May to September bring 56% of it.

The nearest other station, Shabbona 5 NNE, IL, 6 miles south of Malta, has a last frost 4 days later (April 28), a first frost 8 days earlier (October 10), a season 14 days shorter.

The first measurable snow (0.1 inch or more) in Malta usually arrives around November 17, and the last of the season around March 26. Those are the middle dates across the winters of 1991–2020 at De Kalb, IL, 5.5 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 29 days after the last snow.

ZIP 60150 is 6 miles from De Kalb, IL, which stands at 873 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 60115 (Dekalb). The 2023 USDA Plant Hardiness Zone Map lists ZIP 60150 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.