Frost Dates for 49094 — Union City, Michigan

Half of springs at Coldwater St School, MI see their last 32°F night by May 2; only one in ten is past it by April 18, and one in ten still has one after May 18. Planting tender crops after May 9 leaves a 30% risk of a frost on them, after May 13 20%, and after May 18 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 13 in half of years, as early as September 30 one year in ten, and holds off past October 30 one year in ten. A hard freeze of 28°F follows 15 days later, around October 28; in spring the one-in-ten date for 28°F is May 8, 10 days before the 32°F one. The freeze-free season lasts 163 days in a typical year, longer than at 62% of the 172 Michigan stations; it reaches 182 days one year in ten and falls short of 142 one year in ten. On average 136 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 14, and return around October 2. Severe cold of 16°F or below comes every winter, usually between November 29 and March 21.

July is the warmest month at Coldwater St School, MI, averaging 82°F by day and 60°F at night; January is the coldest at 31°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 57% of years.

Warmth for growing adds up to 2,638 growing degree days a year (base 50°F), more than at 66% of the 172 Michigan stations. 34% of them (900) have built up by the end of June, and July adds the most, 648. Precipitation totals 39.2 inches a year, most in August (4.4") and least in March (2.2"); May to September bring 51% of it.

The nearest other station, Battle Creek Kellogg Airport, MI, 18 miles north of Union City, has a last frost 2 days earlier (April 30), a first frost 6 days later (October 19), a season 7 days longer.

The first measurable snow (0.1 inch or more) in Union City usually arrives around November 21, and the last of the season around March 19. Those are the middle dates across the winters of 1991–2020 at Coldwater St School, MI, 9.5 miles away: half of years saw snow earlier, half later. Snow fell in 97% of those winters. The last 32°F night of spring typically comes 44 days after the last snow.

ZIP 49094 is 10 miles from Coldwater St School, MI, which stands at 984 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 5 other ZIP codes share the station; its figures are presented in full for 49036 (Coldwater). The 2023 USDA Plant Hardiness Zone Map lists ZIP 49094 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.