Frost Dates for 60030 — Grayslake, Illinois

Half of springs at Mundelein 4 WSW, IL see their last 32°F night by April 29; only one in ten is past it by April 14, and one in ten still has one after May 15. Planting tender crops after May 5 leaves a 30% risk of a frost on them, after May 9 20%, and after May 15 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 20 in half of years, as early as October 4 one year in ten, and holds off past November 1 one year in ten. A hard freeze of 28°F follows 11 days later, around October 31; in spring the one-in-ten date for 28°F is May 4, 11 days before the 32°F one. The freeze-free season lasts 172 days in a typical year, shorter than at 82% of the 158 Illinois stations; it reaches 193 days one year in ten and falls short of 150 one year in ten. On average 140 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 10, and return around October 9. Severe cold of 16°F or below comes every winter, usually between November 28 and March 15.

July is the warmest month at Mundelein 4 WSW, IL, averaging 82°F by day and 62°F at night; January is the coldest at 29°F and 14°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 45% of years.

Warmth for growing adds up to 2,783 growing degree days a year (base 50°F), fewer than at 94% of the 158 Illinois stations. 32% of them (895) have built up by the end of June, and July adds the most, 688. Precipitation totals 38.6 inches a year, most in May (4.6") and least in January (1.8"); May to September bring 53% of it.

The nearest other station, Lake Villa 2NE, IL, 6 miles north of Grayslake, has a last frost 5 days earlier (April 24), a first frost 3 days later (October 23), a season 8 days longer.

The first measurable snow (0.1 inch or more) in Grayslake usually arrives around November 23, and the last of the season around April 6. Those are the middle dates across the winters of 1991–2020 at Mundelein 4 WSW, IL, 6.2 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 23 days after the last snow.

ZIP 60030 is 6 miles from Mundelein 4 WSW, IL, which stands at 840 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 60047 (Lake Zurich). The 2023 USDA Plant Hardiness Zone Map lists ZIP 60030 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.