Frost Dates for 56209 — Atwater, Minnesota

Half of springs at Willmar Wwtp, MN see their last 32°F night by April 30; only one in ten is past it by April 16, and one in ten still has one after May 13. Planting tender crops after May 4 leaves a 30% risk of a frost on them, after May 8 20%, and after May 13 10%. The 13 days between the even-odds date and the one-in-ten date is narrower than at 61% of the 142 Minnesota stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 7 in half of years, as early as September 23 one year in ten, and holds off past October 21 one year in ten. A hard freeze of 28°F follows 12 days later, around October 19; in spring the one-in-ten date for 28°F is May 2, 11 days before the 32°F one. The freeze-free season lasts 159 days in a typical year, longer than at 74% of the 142 Minnesota stations; it reaches 178 days one year in ten and falls short of 142 one year in ten. On average 166 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 9 days longer, to about May 9, and return around September 29. Severe cold of 16°F or below comes every winter, usually between November 13 and March 26.

July is the warmest month at Willmar Wwtp, MN, averaging 82°F by day and 62°F at night; January is the coldest at 21°F and 3°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 46% of years.

Warmth for growing adds up to 2,547 growing degree days a year (base 50°F), more than at 65% of the 142 Minnesota stations. 33% of them (849) have built up by the end of June, and July adds the most, 673. Precipitation totals 28.6 inches a year, most in June (4.8") and least in January (0.7"); May to September bring 65% of it.

The nearest other station, Litchfield, MN, 12 miles east of Atwater, has a last frost 6 days later (May 6), a first frost 5 days earlier (October 2), a season 12 days shorter.

The first measurable snow (0.1 inch or more) in Atwater usually arrives around November 6, and the last of the season around April 9. Those are the middle dates across the winters of 1991–2020 at Willmar Wwtp, MN, 12 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 21 days after the last snow.

ZIP 56209 is 12 miles from Willmar Wwtp, MN, which stands at 1,100 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 56201 (Willmar). The 2023 USDA Plant Hardiness Zone Map lists ZIP 56209 in zone 4b, the band where the coldest night of the year averaged -25 to -20°F (-31.7 to -28.9°C) over 1991–2020; a zone describes winter lows, not frost dates.