Frost Dates for 59718 — Bozeman, Montana

Half of springs at Bozeman 6 W Exp Farm, MT see their last 32°F night by May 23; only one in ten is past it by May 5, and one in ten still has one after June 12. Planting tender crops after May 31 leaves a 30% risk of a frost on them, after June 5 20%, and after June 12 10%. The 20 days between the even-odds date and the one-in-ten date is wider than at 84% of the 68 Montana stations behind this site's ZIP pages.

In fall the first 32°F night comes by September 23 in half of years, as early as September 4 one year in ten, and holds off past October 6 one year in ten. A hard freeze of 28°F follows 10 days later, around October 3; in spring the one-in-ten date for 28°F is May 18, 25 days before the 32°F one. The freeze-free season lasts 123 days in a typical year, shorter than at 56% of the 68 Montana stations; it reaches 144 days one year in ten and falls short of 96 one year in ten. On average 180 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 21 days longer, to about June 13, and return around September 9. Severe cold of 16°F or below comes every winter, usually between November 3 and March 29.

July is the warmest month at Bozeman 6 W Exp Farm, MT, averaging 83°F by day and 51°F at night; December is the coldest at 34°F and 15°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 29% of years.

Warmth for growing adds up to 1,751 growing degree days a year (base 50°F), fewer than at 68% of the 68 Montana stations. 25% of them (433) have built up by the end of June, and July adds the most, 521. Precipitation totals 15.9 inches a year, most in June (2.8") and least in January (0.5"); May to September bring 57% of it.

The nearest other station, Bozeman Montana State Univ, MT, 5 miles east of Bozeman, has a last frost 3 days later (May 26), a first frost 1 day earlier (September 22), a season 7 days shorter.

The first measurable snow (0.1 inch or more) in Bozeman usually arrives around October 7, and the last of the season around May 11. Those are the middle dates across the winters of 1991–2020 at Bozeman Montana State Univ, MT, 4.6 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 12 days after the last snow.

ZIP 59718 is 1 mile from Bozeman 6 W Exp Farm, MT, which stands at 4,775 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 1 other ZIP code shares the station. The 2023 USDA Plant Hardiness Zone Map lists ZIP 59718 in zone 5a, the band where the coldest night of the year averaged -20 to -15°F (-28.9 to -26.1°C) over 1991–2020; a zone describes winter lows, not frost dates.