Frost Dates for 48656 — Saint Helen, Michigan

Half of springs at Houghton Lk Roscommon Airport, MI see their last 32°F night by May 19; only one in ten is past it by April 30, and one in ten still has one after June 3. Planting tender crops after May 27 leaves a 30% risk of a frost on them, after May 30 20%, and after June 3 10%. The 15 days between the even-odds date and the one-in-ten date is narrower than at 55% of the 172 Michigan stations behind this site's ZIP pages.

In fall the first 32°F night comes by September 23 in half of years, as early as September 6 one year in ten, and holds off past October 7 one year in ten. A hard freeze of 28°F follows 12 days later, around October 5; in spring the one-in-ten date for 28°F is May 24, 10 days before the 32°F one. The freeze-free season lasts 125 days in a typical year, shorter than at 91% of the 172 Michigan stations; it reaches 150 days one year in ten and falls short of 100 one year in ten. On average 169 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 15 days longer, to about June 3, and return around September 8. Severe cold of 16°F or below comes every winter, usually between November 21 and April 2.

July is the warmest month at Houghton Lk Roscommon Airport, MI, averaging 81°F by day and 55°F at night; January is the coldest at 27°F and 11°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 87% of years and June still brings one in 16% of years.

Warmth for growing adds up to 2,035 growing degree days a year (base 50°F), fewer than at 76% of the 172 Michigan stations. 32% of them (656) have built up by the end of June, and July adds the most, 550. Precipitation totals 29.7 inches a year, most in May (3.2") and least in February (1.4"); May to September bring 49% of it.

The nearest other station, W Branch 3SE, MI, 14 miles southeast of Saint Helen and 266 feet lower, has a last frost 4 days earlier (May 15), a first frost 11 days later (October 4), a season 18 days longer.

The first measurable snow (0.1 inch or more) in Saint Helen usually arrives around November 9, and the last of the season around April 12. Those are the middle dates across the winters of 1991–2020 at Houghton Lk Roscommon Airport, MI, 11.6 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 37 days after the last snow.

ZIP 48656 is 12 miles from Houghton Lk Roscommon Airport, MI, which stands at 1,151 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 2 other ZIP codes share the station; its figures are presented in full for 48653 (Roscommon). The 2023 USDA Plant Hardiness Zone Map lists ZIP 48656 in zone 5a, the band where the coldest night of the year averaged -20 to -15°F (-28.9 to -26.1°C) over 1991–2020; a zone describes winter lows, not frost dates.