Frost Dates for 49452 — Rothbury, Michigan

Half of springs at Montague 4 NW, MI see their last 32°F night by May 19; only one in ten is past it by May 1, and one in ten still has one after June 6. Planting tender crops after May 27 leaves a 30% risk of a frost on them, after May 31 20%, and after June 6 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 4 in half of years, as early as September 16 one year in ten, and holds off past October 20 one year in ten. A hard freeze of 28°F follows 14 days later, around October 18; in spring the one-in-ten date for 28°F is May 26, 11 days before the 32°F one. The freeze-free season lasts 136 days in a typical year, shorter than at 77% of the 172 Michigan stations; it reaches 162 days one year in ten and falls short of 112 one year in ten. On average 145 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 31, and return around September 23. Severe cold of 16°F or below comes every winter, usually between December 5 and March 28.

July is the warmest month at Montague 4 NW, MI, averaging 79°F by day and 58°F at night; January is the coldest at 30°F and 19°F. A freezing night is all but certain in every month from October to April (a 90% chance or more). From July to August the chance of a 32°F night stays under 10% each month. In spring, May still brings one in 89% of years and June still brings one in 19% of years.

Warmth for growing adds up to 2,270 growing degree days a year (base 50°F), fewer than at 58% of the 172 Michigan stations. 30% of them (690) have built up by the end of June, and July adds the most, 578. Precipitation totals 35.4 inches a year, most in October (4.1") and least in February (1.4"); May to September bring 46% of it.

The nearest other station, Hesperia 4 WNW, MI, 10 miles northeast of Rothbury, has a last frost 2 days earlier (May 17), a first frost 3 days earlier (October 1), a season 1 day longer.

The first measurable snow (0.1 inch or more) in Rothbury usually arrives around November 17, and the last of the season around March 24. Those are the middle dates across the winters of 1991–2020 at Montague 4 NW, MI, 8.3 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 56 days after the last snow.

ZIP 49452 is 8 miles from Montague 4 NW, MI, which stands at 650 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 3 other ZIP codes share the station; its figures are presented in full for 49461 (Whitehall). The 2023 USDA Plant Hardiness Zone Map lists ZIP 49452 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.