Frost Dates for 56435 — Backus, Minnesota

Half of springs at Deep Portage, MN see their last 32°F night by May 5; only one in ten is past it by April 24, and one in ten still has one after May 19. Planting tender crops after May 11 leaves a 30% risk of a frost on them, after May 14 20%, and after May 19 10%. The 14 days between the even-odds date and the one-in-ten date is narrower than at 37% of the 142 Minnesota stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 5 in half of years, as early as September 22 one year in ten, and holds off past October 20 one year in ten. A hard freeze of 28°F follows 13 days later, around October 18; in spring the one-in-ten date for 28°F is May 8, 11 days before the 32°F one. The freeze-free season lasts 150 days in a typical year, shorter than at 51% of the 142 Minnesota stations; it reaches 170 days one year in ten and falls short of 131 one year in ten. On average 179 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 16, and return around September 25. Severe cold of 16°F or below comes every winter, usually between November 13 and April 2.

July is the warmest month at Deep Portage, MN, averaging 80°F by day and 59°F at night; January is the coldest at 19°F and 1°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 71% of years.

Warmth for growing adds up to 2,143 growing degree days a year (base 50°F), fewer than at 70% of the 142 Minnesota stations. 32% of them (688) have built up by the end of June, and July adds the most, 598.

The nearest other station, Walker, MN, 19 miles north of Backus, has a last frost 1 day earlier (May 4), a first frost 2 days later (October 7), a season 5 days longer.

The first measurable snow (0.1 inch or more) in Backus usually arrives around November 10, and the last of the season around April 5. Those are the middle dates across the winters of 1991–2020 at Deep Portage, MN, 7.6 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 30 days after the last snow.

ZIP 56435 is 8 miles from Deep Portage, MN, which stands at 1,471 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 1 other ZIP code shares the station; its figures are presented in full for 56474 (Pine River). The 2023 USDA Plant Hardiness Zone Map lists ZIP 56435 in zone 4a, the band where the coldest night of the year averaged -30 to -25°F (-34.4 to -31.7°C) over 1991–2020; a zone describes winter lows, not frost dates.