Frost Dates for 59022 — Crow Agency, Montana

Half of springs at Hardin, MT see their last 32°F night by May 13; only one in ten is past it by April 30, and one in ten still has one after May 26. Planting tender crops after May 19 leaves a 30% risk of a frost on them, after May 22 20%, and after May 26 10%. The 13 days between the even-odds date and the one-in-ten date is narrower than at 74% of the 68 Montana stations behind this site's ZIP pages.

In fall the first 32°F night comes by September 29 in half of years, as early as September 14 one year in ten, and holds off past October 10 one year in ten. A hard freeze of 28°F follows 8 days later, around October 7; in spring the one-in-ten date for 28°F is May 13, 13 days before the 32°F one. The freeze-free season lasts 135 days in a typical year, longer than at 66% of the 68 Montana stations; it reaches 154 days one year in ten and falls short of 118 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 12 days longer, to about May 25, and return around September 18. Severe cold of 16°F or below comes every winter, usually between November 2 and March 28.

July is the warmest month at Hardin, MT, averaging 91°F by day and 56°F at night; January is the coldest at 36°F and 11°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 90% of years.

Warmth for growing adds up to 2,597 growing degree days a year (base 50°F), more than at 96% of the 68 Montana stations. 29% of them (761) have built up by the end of June, and July adds the most, 716. Precipitation totals 13.9 inches a year, most in May (2.5") and least in January (0.5"); May to September bring 58% of it.

The nearest other station, Busby, MT, 21 miles east of Crow Agency and 550 feet higher, has a last frost 10 days later (May 23), a first frost 14 days earlier (September 15), a season 22 days shorter.

The first measurable snow (0.1 inch or more) in Crow Agency usually arrives around November 19, and the last of the season around March 23. Those are the middle dates across the winters of 1991–2020 at Hardin, MT, 13.8 miles away: half of years saw snow earlier, half later. Snow fell in 89% of those winters. The last 32°F night of spring typically comes 51 days after the last snow.

ZIP 59022 is 14 miles from Hardin, MT, which stands at 2,880 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 59034 (Hardin). The 2023 USDA Plant Hardiness Zone Map lists ZIP 59022 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.