Frost Dates for 56431 — Aitkin, Minnesota

Half of springs at Aitkin 2E, MN see their last 32°F night by May 16; only one in ten is past it by April 30, and one in ten still has one after June 1. Planting tender crops after May 23 leaves a 30% risk of a frost on them, after May 27 20%, and after June 1 10%. The 16 days between the even-odds date and the one-in-ten date is wider than at 77% of the 142 Minnesota stations behind this site's ZIP pages.

In fall the first 32°F night comes by September 28 in half of years, as early as September 12 one year in ten, and holds off past October 12 one year in ten. A hard freeze of 28°F follows 10 days later, around October 8; in spring the one-in-ten date for 28°F is May 21, 11 days before the 32°F one. The freeze-free season lasts 133 days in a typical year, shorter than at 89% of the 142 Minnesota stations; it reaches 155 days one year in ten and falls short of 112 one year in ten. On average 187 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 28, and return around September 19. Severe cold of 16°F or below comes every winter, usually between November 11 and April 3.

July is the warmest month at Aitkin 2E, MN, averaging 79°F by day and 56°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 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 11% of years.

Warmth for growing adds up to 1,868 growing degree days a year (base 50°F), fewer than at 87% of the 142 Minnesota stations. 30% of them (556) have built up by the end of June, and July adds the most, 546. Precipitation totals 31.8 inches a year, most in July (4.7") and least in February (1.0"); May to September bring 61% of it.

The nearest other station, Isle 12N, MN, 15 miles southeast of Aitkin, has a last frost 6 days earlier (May 10), a first frost 5 days later (October 3), a season 11 days longer.

The first measurable snow (0.1 inch or more) in Aitkin usually arrives around November 2, and the last of the season around April 12. Those are the middle dates across the winters of 1991–2020 at Aitkin 2E, MN, 1.3 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 34 days after the last snow.

ZIP 56431 is 1 mile from Aitkin 2E, MN, which stands at 1,215 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 56431 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.