Frost Dates for 49078 — Otsego, Michigan

Half of springs at Allegan 5NE, MI see their last 32°F night by May 4; only one in ten is past it by April 22, and one in ten still has one after May 22. Planting tender crops after May 11 leaves a 30% risk of a frost on them, after May 17 20%, and after May 22 10%. The 18 days between the even-odds date and the one-in-ten date is wider than at 81% 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 September 30 one year in ten, and holds off past October 29 one year in ten. A hard freeze of 28°F follows 14 days later, around October 29; in spring the one-in-ten date for 28°F is May 10, 12 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 183 days one year in ten and falls short of 139 one year in ten. On average 148 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 13 days longer, to about May 17, and return around October 1. Severe cold of 16°F or below comes every winter, usually between December 5 and March 21.

July is the warmest month at Allegan 5NE, MI, averaging 82°F by day and 58°F at night; January is the coldest at 30°F and 16°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 2,506 growing degree days a year (base 50°F), more than at 52% of the 172 Michigan stations. 33% of them (824) have built up by the end of June, and July adds the most, 614.

The nearest other station, Bloomingdale, MI, 14 miles west of Otsego, has a last frost 3 days later (May 7), a first frost 4 days earlier (October 11), a season 4 days shorter.

The first measurable snow (0.1 inch or more) in Otsego usually arrives around November 18, and the last of the season around March 30. Those are the middle dates across the winters of 1991–2020 at Allegan 5NE, MI, 9.2 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 35 days after the last snow.

ZIP 49078 is 9 miles from Allegan 5NE, MI, which stands at 750 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 7 other ZIP codes share the station; its figures are presented in full for 49010 (Allegan). The 2023 USDA Plant Hardiness Zone Map lists ZIP 49078 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.