Frost dates for 59771Bozeman, MT
The average last spring frost in Bozeman is May 23 and the average first fall frost is September 23, giving a typical growing season of about 123 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 23
- Average first fall frost
- Sep 23
- Growing season
- 123 days
Safer after Jun 12 (1-in-10 risk)
Possible by Sep 4 (1-in-10 risk)
Last frost typically in 209 days
Frost risk by date
NOAA reports frost dates as probabilities. The middle date is the average (a 50% chance). For spring, the 10% date is a safer planting date: frost after it happens in about 1 year in 10. Light frost (36°F) can damage tender plants; a hard freeze (28°F) kills most annuals.
| Temperature | Last spring: 90% / 50% / 10% chance | First fall: 10% / 50% / 90% chance | Growing season (50%) | Years with at least one |
|---|---|---|---|---|
| Light frost (36°F) | May 26 · Jun 13 · Jun 30 | Aug 22 · Sep 9 · Sep 24 | 87 days | 100% |
| Frost / freeze (32°F) | May 5 · May 23 · Jun 12 | Sep 4 · Sep 23 · Oct 6 | 123 days | 100% |
| Hard freeze (28°F) | Apr 20 · May 2 · May 18 | Sep 17 · Oct 3 · Oct 19 | 153 days | 100% |
Planting calendar for Bozeman
Planting windows from the University of Maryland Extension calendar, shifted to your average frost dates. Use them as a starting point and adjust for seed packet instructions and local conditions.
| Crop | Task | Window |
|---|---|---|
| Tomatoes | Start seeds indoors | Apr 22 – Jun 28 |
| Tomatoes | Transplant outdoors | Jun 8 – Jun 3 |
| Peppers | Start seeds indoors | Apr 22 – May 23 |
| Peppers | Transplant outdoors | Jun 22 – Jul 23 |
| Eggplant | Start seeds indoors | May 9 – Jun 7 |
| Eggplant | Transplant outdoors | Jun 22 – Jul 23 |
| Cucumbers | Sow outdoors | Jun 22 – Jun 13 |
| Summer squash | Sow outdoors | Jun 8 – Jul 23 |
| Winter squash & pumpkins | Sow outdoors | Jun 22 – Jul 23 |
| Snap beans | Sow outdoors | Jun 8 – Jul 6 |
| Sweet corn | Sow outdoors | Jun 8 – Jun 3 |
| Watermelon & cantaloupe | Sow outdoors | Jun 22 – Jul 23 |
| Okra | Sow outdoors | Jun 15 – Jul 8 |
| Peas | Sow outdoors (spring) | Apr 22 – Jun 7 |
| Potatoes | Plant outdoors (spring) | Apr 22 – Jun 22 |
| Onions | Start seeds indoors (spring) | Mar 11 – Apr 7 |
| Onions | Transplant outdoors (spring) | May 9 – Jun 7 |
| Broccoli | Start seeds indoors (spring) | Apr 4 – May 8 |
| Broccoli | Transplant outdoors (spring) | May 9 – Jun 7 |
| Broccoli | Start seeds indoors (fall) | May 24 – Jun 3 |
| Broccoli | Transplant outdoors (fall) | Jun 23 – Jul 4 |
| Cabbage | Start seeds indoors (spring) | Mar 25 – Apr 22 |
| Cabbage | Transplant outdoors (spring) | Apr 22 – May 23 |
| Cabbage | Start seeds indoors (fall) | May 14 – Jun 13 |
| Cabbage | Transplant outdoors (fall) | Jun 13 – Jul 14 |
| Leaf lettuce | Sow outdoors (spring) | Apr 22 – Jul 8 |
| Leaf lettuce | Sow outdoors (fall) | Jun 13 – Jul 30 |
| Spinach | Sow outdoors (spring) | Apr 15 – May 29 |
| Spinach | Sow outdoors (fall) | Jun 30 – Aug 4 |
| Radishes | Sow outdoors (spring) | Apr 22 – Jun 12 |
| Radishes | Sow outdoors (fall) | Jun 13 – Aug 14 |
| Kale | Sow outdoors (spring) | May 9 – May 29 |
| Kale | Sow outdoors (fall) | Jun 6 – Jul 14 |
| Carrots | Sow outdoors (spring) | May 23 – Jul 8 |
| Carrots | Sow outdoors (fall) | May 14 – Jun 29 |
| Garlic | Plant outdoors (fall) | Sep 13 – Oct 14 |
Where these dates come from
ZIP code 59771 is matched to the NOAA station Bozeman 6 W Exp Farm, MT, 6.2 km away, at 4,775 ft elevation (178 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Bozeman 6 W Exp Farm, MT (used) | 4,775 ft | May 23 | Sep 23 |
| Bozeman Gallatin Fld, MT | 4,427 ft | May 26 | Sep 16 |
| Bozeman Montana State Univ, MT | 4,913 ft | May 26 | Sep 22 |
| Logan Landfill, MT | 4,243 ft | May 26 | Sep 15 |
Frost dates near Bozeman
- Belgrade, MT 59714 · last May 26, first Sep 16
- Bozeman, MT 59715 · last May 26, first Sep 22
- Manhattan, MT 59741 · last May 26, first Sep 16
- Three Forks, MT 59752 · last May 9, first Sep 27
- Willow Creek, MT 59760 · last May 9, first Sep 27
- Clyde Park, MT 59018 · last May 27, first Sep 14
- Gallatin Gateway, MT 59730 · last —, first —
- Livingston, MT 59047 · last May 27, first Sep 14
Frequently asked questions
- When is the last frost in Bozeman, MT?
- For ZIP code 59771, the average last spring frost (32°F) is May 23, based on NOAA 1991-2020 climate normals for the Bozeman 6 W Exp Farm, MT weather station. There is a 1-in-10 chance of a frost after June 12.
- When is the first frost in Bozeman, MT?
- The average first fall frost (32°F) is September 23. There is a 1-in-10 chance of frost by September 4, so tender plants are at risk from that point on.
- How long is the growing season in 59771?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 123 days long.
- Are these frost dates a forecast?
- No. They are 30-year averages and probabilities from NOAA weather station records. Use them to plan, then watch your local forecast before planting tender crops or leaving them uncovered.