Frost Dates for 49221 — Adrian, Michigan

Half of springs at Adrian 2 NNE, MI see their last 32°F night by May 1; only one in ten is past it by April 18, and one in ten still has one after May 17. Planting tender crops after May 8 leaves a 30% risk of a frost on them, after May 12 20%, and after May 17 10%. The 16 days between the even-odds date and the one-in-ten date is narrower than at 38% of the 172 Michigan stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 15 in half of years, as early as October 1 one year in ten, and holds off past October 29 one year in ten. A hard freeze of 28°F follows 12 days later, around October 27; in spring the one-in-ten date for 28°F is May 7, 10 days before the 32°F one. The freeze-free season lasts 164 days in a typical year, longer than at 65% of the 172 Michigan stations; it reaches 185 days one year in ten and falls short of 143 one year in ten. On average 142 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 13, and return around October 3. Severe cold of 16°F or below comes every winter, usually between November 30 and March 18.

July is the warmest month at Adrian 2 NNE, MI, averaging 85°F by day and 60°F at night; January is the coldest at 33°F and 17°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 52% of years.

Warmth for growing adds up to 2,861 growing degree days a year (base 50°F), more than at 85% of the 172 Michigan stations. 34% of them (959) have built up by the end of June, and July adds the most, 697. Precipitation totals 36.7 inches a year, most in June (4.1") and least in February (2.0"); May to September bring 50% of it.

The nearest other station, Adrian Lenawee Co Airport, MI, 3 miles southwest of Adrian, has a last frost 4 days earlier (April 27), a first frost 5 days later (October 20), a season 9 days longer.

The first measurable snow (0.1 inch or more) in Adrian 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 Adrian 2 NNE, MI, 1.9 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 41 days after the last snow.

ZIP 49221 is 2 miles from Adrian 2 NNE, MI, which stands at 760 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 49221 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.