Frost Dates for 49241 — Hanover, Michigan

Half of springs at Hillsdale, MI see their last 32°F night by May 3; only one in ten is past it by April 20, and one in ten still has one after May 19. Planting tender crops after May 10 leaves a 30% risk of a frost on them, after May 14 20%, and after May 19 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 12 in half of years, as early as September 29 one year in ten, and holds off past October 27 one year in ten. A hard freeze of 28°F follows 14 days later, around October 26; in spring the one-in-ten date for 28°F is May 9, 10 days before the 32°F one. The freeze-free season lasts 161 days in a typical year, longer than at 56% of the 172 Michigan stations; it reaches 181 days one year in ten and falls short of 140 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 11 days longer, to about May 14, and return around October 1. Severe cold of 16°F or below comes every winter, usually between November 30 and March 22.

July is the warmest month at Hillsdale, MI, averaging 83°F by day and 60°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 60% of years.

Warmth for growing adds up to 2,649 growing degree days a year (base 50°F), more than at 66% of the 172 Michigan stations. 34% of them (890) have built up by the end of June, and July adds the most, 657. Precipitation totals 39.6 inches a year, most in May (4.6") and least in February (2.3"); May to September bring 49% of it.

The nearest other station, Jackson Reynolds Field, MI, 13 miles northeast of Hanover, has a last frost 2 days earlier (May 1), a first frost 2 days later (October 14), a season 3 days longer.

The first measurable snow (0.1 inch or more) in Hanover usually arrives around November 18, and the last of the season around April 2. Those are the middle dates across the winters of 1991–2020 at Hillsdale, MI, 12.1 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 31 days after the last snow.

ZIP 49241 is 12 miles from Hillsdale, MI, which stands at 1,080 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 49242 (Hillsdale). The 2023 USDA Plant Hardiness Zone Map lists ZIP 49241 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.