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Frost dates / Montana / Bozeman

Frost dates in Bozeman, MT

The station on this page is BOZEMAN MONTANA STATE UNIV, MT US (USC00241044), 1.5 miles from the city point. Population in the Census 2024 estimate is 57,894.

Zone 5aUSDA average annual extreme minimum -20°F to -15°F, from ZIP 59718 (6.4 miles from the city point used on this page).

Median last 32°F is May 26. Median first 32°F is September 22. The 50% growing-season length is 116 days. The green band runs from the median last frost to the median first frost. Thin ticks mark the 10%, 50%, and 90% dates.

Outside the median season Growing seasonTicks: 10%, 50%, and 90%

Last 32°F in spring

NCEI’s probability is the chance the last spring minimum of 32°F or lower occurs on or after the date.

ProbabilityDateHow to read it
90%May 9Earlier date. A last 32°F on or after this day is common.
50%May 26Median.
10%June 14Later date. A last 32°F on or after this day is uncommon.

First 32°F in fall

NCEI’s probability is the chance the first autumn minimum of 32°F or lower occurs on or before the date.

ProbabilityDateHow to read it
10%September 5Earlier date. A first 32°F on or before this day is uncommon.
50%September 22Median.
90%October 5Later date. A first 32°F on or before this day is common.

32°F growing-season length

Days between the last spring 32°F and the first autumn 32°F. The figure is a length the season meets or exceeds at that probability, from NCEI, not a subtraction done on this site.

Probability the season is at least this longDays
10%139
50%116
90%93

28°F threshold

10%50%90%
Last, on or afterMay 26May 8April 23
First, on or beforeSeptember 18October 3October 19
Season at least167 days147 days125 days

36°F threshold

10%50%90%
Last, on or afterJune 28June 14May 28
First, on or beforeAugust 26September 8September 23
Season at least108 days87 days66 days

Station BOZEMAN MONTANA STATE UNIV, MT US (USC00241044). Completeness flag S, 30 years used for the 32°F dates. NCEI’s annual probability of at least one day at or below 32°F is 100%. Freeze dates are conditional on that threshold occurring. Elevation 1497.5 m. The same probability language applies to the 28°F and 36°F rows when those dates passed the same quality checks.

Check a crop against this station

Bozeman, MT

Zone 5aAverage annual extreme minimum -20°F to -15°F

Median last 32°F is May 26. Median first 32°F is September 22. The 50% growing-season length is 116 days. The green band runs from the median last frost to the median first frost. Thin ticks mark the 10%, 50%, and 90% dates.

Outside the median season Growing seasonTicks: 10%, 50%, and 90%

Montana. Nearest qualified station: BOZEMAN MONTANA STATE UNIV, MT US (USC00241044), 1.5 miles. Median last 32°F May 26. Median first 32°F September 22. The 50% growing-season length is 116 days.

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32°F probabilities at this station
10%50%90%
Last 32°F on or afterJune 14May 26May 9
First 32°F on or beforeSeptember 5September 22October 5

Column order matches the NCEI file: for the last freeze, 10% is the later date and 90% is the earlier date. How to read the probabilities.

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Planting calendar

Frost dates for Montana are above. Planting windows appear for states with a cited extension guide. The fall and seed tools use the numbers you enter and the station dates.

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