Frost Dates for 56342 — Isle, Minnesota

Half of springs at Isle 12N, MN see their last 32°F night by May 10; only one in ten is past it by April 27, and one in ten still has one after May 28. Planting tender crops after May 17 leaves a 30% risk of a frost on them, after May 22 20%, and after May 28 10%. The 18 days between the even-odds date and the one-in-ten date is wider than at 92% of the 142 Minnesota stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 3 in half of years, as early as September 19 one year in ten, and holds off past October 17 one year in ten. A hard freeze of 28°F follows 13 days later, around October 16; in spring the one-in-ten date for 28°F is May 12, 16 days before the 32°F one. The freeze-free season lasts 144 days in a typical year, shorter than at 67% of the 142 Minnesota stations; it reaches 164 days one year in ten and falls short of 124 one year in ten. On average 176 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 14 days longer, to about May 24, and return around September 24. Severe cold of 16°F or below comes every winter, usually between November 13 and April 3.

July is the warmest month at Isle 12N, MN, averaging 78°F by day and 58°F at night; January is the coldest at 19°F and 0°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 80% of years.

Warmth for growing adds up to 2,024 growing degree days a year (base 50°F), fewer than at 80% of the 142 Minnesota stations. 30% of them (608) have built up by the end of June, and July adds the most, 566. Precipitation totals 28.9 inches a year, most in July (4.4") and least in January (0.6"); May to September bring 65% of it.

The nearest other station, Sandstone 6 W, MN, 23 miles east of Isle and 155 feet lower, has a last frost 3 days later (May 13), a first frost 4 days earlier (September 29), a season 7 days shorter.

The first measurable snow (0.1 inch or more) in Isle usually arrives around November 10, and the last of the season around April 12. Those are the middle dates across the winters of 1991–2020 at Isle 12N, MN, 7.7 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 28 days after the last snow.

ZIP 56342 is 8 miles from Isle 12N, MN, which stands at 1,285 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 56359 (Onamia). The 2023 USDA Plant Hardiness Zone Map lists ZIP 56342 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.