Frost Dates for 59715 — Bozeman, Montana

Half of springs at Bozeman Montana State Univ, MT see their last 32°F night by May 26; only one in ten is past it by May 9, and one in ten still has one after June 14. Planting tender crops after June 3 leaves a 30% risk of a frost on them, after June 8 20%, and after June 14 10%. The 19 days between the even-odds date and the one-in-ten date is wider than at 78% of the 68 Montana stations behind this site's ZIP pages.

In fall the first 32°F night comes by September 22 in half of years, as early as September 5 one year in ten, and holds off past October 5 one year in ten. A hard freeze of 28°F follows 11 days later, around October 3; in spring the one-in-ten date for 28°F is May 26, 19 days before the 32°F one. The freeze-free season lasts 116 days in a typical year, shorter than at 69% of the 68 Montana stations; it reaches 139 days one year in ten and falls short of 93 one year in ten. On average 178 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 19 days longer, to about June 14, and return around September 8. Severe cold of 16°F or below comes every winter, usually between November 1 and April 1.

July is the warmest month at Bozeman Montana State Univ, MT, averaging 82°F by day and 52°F at night; December is the coldest at 33°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 37% of years.

Warmth for growing adds up to 1,719 growing degree days a year (base 50°F), fewer than at 71% of the 68 Montana stations. 24% of them (415) have built up by the end of June, and July adds the most, 524. Precipitation totals 19.9 inches a year, most in June (3.3") and least in February (0.8"); May to September bring 51% of it.

The nearest other station, Bozeman 6 W Exp Farm, MT, 8 miles west of Bozeman, has a last frost 3 days earlier (May 23), a first frost 1 day later (September 23), a season 7 days longer.

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, 4.2 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 15 days after the last snow.

ZIP 59715 is 4 miles from Bozeman Montana State Univ, MT, which stands at 4,913 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 59715 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.