Frost Dates for 55604 — Grand Marais, Minnesota

Half of springs at Grand Marais, MN see their last 32°F night by May 22; only one in ten is past it by May 3, and one in ten still has one after June 18. Planting tender crops after June 2 leaves a 30% risk of a frost on them, after June 10 20%, and after June 18 10%. The 27 days between the even-odds date and the one-in-ten date is the widest of the 142 Minnesota stations behind this site's ZIP pages, so a fixed calendar date is a gamble here.

In fall the first 32°F night comes by October 9 in half of years, as early as September 25 one year in ten, and holds off past October 25 one year in ten. A hard freeze of 28°F follows 15 days later, around October 24; in spring the one-in-ten date for 28°F is June 8, 10 days before the 32°F one. The freeze-free season lasts 136 days in a typical year, shorter than at 85% of the 142 Minnesota stations; it reaches 163 days one year in ten and falls short of 109 one year in ten. On average 170 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 June 3, and return around September 29. Severe cold of 16°F or below comes every winter, usually between November 18 and April 2.

August is the warmest month at Grand Marais, MN, averaging 70°F by day and 54°F at night; January is the coldest at 24°F and 7°F. A freezing night is all but certain in every month from October to May (a 90% chance or more). From July to August the chance of a 32°F night stays under 10% each month. In spring, June still brings one in 33% of years.

Warmth for growing adds up to 1,045 growing degree days a year (base 50°F), the fewest of the 142 Minnesota stations. 13% of them (139) have built up by the end of June, and August adds the most, 371. Precipitation totals 25.9 inches a year, most in June (3.7") and least in January (0.8"); May to September bring 56% of it.

The first measurable snow (0.1 inch or more) in Grand Marais usually arrives around November 21, and the last of the season around April 4. Those are the middle dates across the winters of 1991–2020 at Grand Marais, MN, 16.4 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 48 days after the last snow.

ZIP 55604 is 16 miles from Grand Marais, MN, which stands at 610 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 55604 in zone 3b, the band where the coldest night of the year averaged -35 to -30°F (-37.2 to -34.4°C) over 1991–2020; a zone describes winter lows, not frost dates.