Frost dates · USDA zone 5a
Frost dates for Bozeman, MT
Bozeman, MT sees its last 32 °F night of spring around May 23 and its first of fall around September 23 — a 123-day freeze-free season in a typical year.
Pick a sauce; the Plan Builder runs this station's dates and hands back the calendar, plant count and gear list.
Freeze odds, by date
| Odds | Last spring freeze after | First fall freeze before |
|---|---|---|
| 9 years in 10 | May 5 | Oct 6 |
| Median — 1 year in 2 | May 23 | Sep 23 |
| 1 year in 10 | Jun 12 | Sep 4 |
The top row is the risky edge: in 9 years of 10 a spring freeze still comes after it, so tender transplants set out then need cover. The bottom row is the cautious date — only 1 year in 10 freezes after it — and the one to plan uncovered tender transplants against. Freeze-free season: 123 days median, at least 96 in 9 years of 10, at least 144 days in 1 year of 10. NOAA ranks season length year by year, so it is not the gap between two rows above. A hard freeze (28 °F) has a median last date of May 2 and first of Oct 3.
Bozeman planting calendar, 2027
Every row runs from the median last frost (May 23) and median first frost (Sep 23) above, using each cultivar's days to maturity. Same engine as the Plan Builder.
| Crop | Start indoors | Transplant / plant | First harvest | Days |
|---|---|---|---|---|
| Hardneck GarlicSiberian (porcelain hardneck) | — | Oct 15prior fall | Jun 12 | 240 from sow |
| Spanish OnionYellow Sweet Spanish (long-day) | Feb 28 | Apr 25 | Aug 13 | 110 from transplant |
| Mustard greensGarnet Giant (Brassica juncea) | Direct sow | May 23 | Jun 22 | 30 from sow |
| CilantroSlow Bolt (Coriandrum sativum) | May 9 | May 9 | Jun 23 | 45 from sow |
| Genovese BasilGenovese | Apr 25 | Jun 6 | Aug 5 | 60 from transplant |
| CayenneLong Slim Cayenne (Capsicum annuum) | Mar 28 | May 30 | Aug 13 | 75 from transplant |
| HabaneroOrange Habanero (Capsicum chinense) | Mar 14 | Jun 6 | Sep 9 | 95 from transplant |
| JalapeñoEarly Jalapeño (Capsicum annuum) | Mar 28 | May 30 | Aug 13 | 75 from transplant |
| Marconi Red PepperMarconi Red (Capsicum annuum) | Mar 28 | May 30 | Aug 18 | 80 from transplant |
| SerranoSerrano Tampiqueño (Capsicum annuum) | Mar 28 | May 30 | Aug 18 | 80 from transplant |
| Nantes CarrotScarlet Nantes | May 9 | May 9 | Jul 18 | 70 from sow |
| TomatilloToma Verde | Apr 11 | May 30 | Aug 8 | 70 from transplant |
| Roma TomatoRoma VF (determinate paste) | Apr 11 | May 30 | Aug 13 | 75 from transplant |
| San Marzano TomatoSan Marzano (indeterminate paste) | Apr 11 | May 30 | Aug 18 | 80 from transplant |
Tight means first harvest lands within two weeks of the median first fall frost: start that crop indoors on time or cover it in fall.
What sauce can Bozeman grow?
Each sauce, scheduled for a Bozeman container garden: when the first seeds go in and when enough fruit has ripened for one batch.
Bozeman frost questions
When is the last frost in Bozeman, MT?
The median last 32 °F freeze at BOZEMAN 6 W EXP FARM, MT is May 23: half of years see a later one. One year in ten, a freeze still comes after June 12; nine years in ten, it comes after May 5. Source: NOAA NCEI 1991–2020 U.S. Climate Normals.
When is the first frost in Bozeman, MT?
The median first 32 °F freeze of fall is September 23. One year in ten it arrives before September 4; nine years in ten, before October 6.
How long is the growing season in Bozeman, MT?
123 days between the last spring and first fall 32 °F freeze in a median year. Nine years in ten the season runs at least 96 days; one year in ten, at least 144 days.
What growing zone is Bozeman, MT?
USDA hardiness zone 5a, per the 2023 USDA Plant Hardiness Zone Map for ZIP 59718. A zone describes the coldest winter night, not when frost ends, so it is the wrong number for a planting calendar — the frost dates on this page are the right one.
When should I plant tomatoes in Bozeman, MT?
Start Roma VF (determinate paste) seeds indoors around Apr 11 and transplant around May 30, 1 week after the median last frost. To cut the freeze risk to one year in ten, wait for Jun 12. First ripe fruit lands around Aug 13.
When should I plant peppers in Bozeman, MT?
Sow jalapeño indoors on a heat mat around Mar 28; transplant no earlier than May 30, and wait past it until nights hold above 50 °F — that can run weeks later. First green pods around Aug 13.
Nearby in Montana
- Billingslast frost May 5
- Great Fallslast frost May 6
- Missoulalast frost May 10
All Montana frost dates → · How frost-date math drives a sowing calendar →