Frost Dates for 48817 — Corunna, Michigan

Half of springs at Corunna 2 NE, MI see their last 32°F night by May 5; only one in ten is past it by April 20, and one in ten still has one after May 20. Planting tender crops after May 10 leaves a 30% risk of a frost on them, after May 15 20%, and after May 20 10%. The 15 days between the even-odds date and the one-in-ten date is narrower than at 55% of the 172 Michigan stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 14 in half of years, as early as September 29 one year in ten, and holds off past October 29 one year in ten. A hard freeze of 28°F follows 15 days later, around October 29; in spring the one-in-ten date for 28°F is May 10, 10 days before the 32°F one. The freeze-free season lasts 160 days in a typical year, longer than at 51% of the 172 Michigan stations; it reaches 181 days one year in ten and falls short of 141 one year in ten. On average 155 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 17, and return around October 1. Severe cold of 16°F or below comes every winter, usually between December 1 and March 19.

July is the warmest month at Corunna 2 NE, MI, averaging 83°F by day and 59°F at night; January is the coldest at 31°F and 15°F. A freezing night is all but certain in every month from October to April (a 90% chance or more). From June to August the chance of a 32°F night stays under 10% each month. In spring, May still brings one in 64% of years.

Warmth for growing adds up to 2,579 growing degree days a year (base 50°F), more than at 60% of the 172 Michigan stations. 32% of them (834) have built up by the end of June, and July adds the most, 648. Precipitation totals 33.7 inches a year, most in May (4.0") and least in February (1.8"); May to September bring 49% of it.

The nearest other station, Owosso Wwtp, MI, 6 miles west of Corunna, has a last frost 4 days earlier (May 1), a first frost 1 day later (October 15), a season 4 days longer.

The first measurable snow (0.1 inch or more) in Corunna usually arrives around November 25, and the last of the season around March 29. Those are the middle dates across the winters of 1991–2020 at Owosso Wwtp, MI, 6 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 37 days after the last snow.

ZIP 48817 is under a mile from Corunna 2 NE, MI, which stands at 762 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 1 other ZIP code shares the station. The 2023 USDA Plant Hardiness Zone Map lists ZIP 48817 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.