When to plant in Butte-Silver Bow, MT
USDA Zone 5aEverything below — frost dates, hardiness zone, and what to plant when in Butte-Silver Bow, Montana — is derived from the closest NOAA station with complete climate normals.
A ~84-day frost-free window makes Butte-Silver Bow a short-season garden: choose early varieties and start long-season crops indoors well ahead of the last frost. In zone 5a, Butte-Silver Bow gardeners can grow many hardy perennials, while the last and first frost still dictate the annual vegetable calendar.
Frost probability
BUTTE BERT MOONEY AP · 1991–2020The date the last spring and first fall frost occur, by threshold and probability. A 90% date is later in spring — and earlier in fall — than a 10% date; the 50% · 32°F row is what most gardeners plan around. These are Butte-Silver Bow’s own odds, recorded at BUTTE BERT MOONEY AP.
| Threshold | SPRING 10% | SPRING 50% | SPRING 90% | FALL 10% | FALL 50% | FALL 90% |
|---|---|---|---|---|---|---|
| 32°F | Jul 1 | Jun 13 | May 27 | Aug 24 | Sep 5 | Sep 19 |
| 28°F | Jun 10 | May 21 | May 8 | Sep 2 | Sep 17 | Oct 1 |
Download this table as CSV ↓ — every threshold and probability, plus this city’s planting-window dates.
What to plant now
TODAY · JULY 19Full-year planting calendar
Each bar is the exact window to take a planting action in Butte-Silver Bow, drawn to the day from the local frost dates. The dashed line is today.
Nearby weather stations
3 within 34 km · complete 32°F normalsWhen stations disagree by more than a few days, that spread is real microclimate variation — elevation, water, urban heat. Judge which station best matches your own yard.
Butte-Silver Bow planting FAQ
When is the last spring frost in Butte-Silver Bow, MT?
Butte-Silver Bow's average last spring frost falls near June 13 — the 50% mark at 32°F in the 1991–2020 normals. Hold tender transplants until the risk has passed, then plant out.
When is the first fall frost in Butte-Silver Bow, MT?
Expect Butte-Silver Bow's first fall frost near September 5 — a 50% chance of 32°F by that date. Bring in or cover tender crops ahead of it.
What hardiness zone is Butte-Silver Bow in?
Butte-Silver Bow is in USDA hardiness zone 5a. In zone 5a, winters are cold — pick cold-hardy varieties and protect tender crops.
How long is the growing season in Butte-Silver Bow?
Butte-Silver Bow has about 84 frost-free days — a short growing season — between the average last spring frost (June 13) and first fall frost (September 5).
When should I plant tomatoes in Butte-Silver Bow?
For Butte-Silver Bow, sow tomatoes indoors about April 18–May 2 and move the seedlings out around June 20, after the last spring frost.
Never miss a window in Butte-Silver Bow
An email when it’s time to start seeds, transplant, and sow — timed to Butte-Silver Bow’s frost dates. Double opt-in, one-click unsubscribe, no spam.
Nearby cities
8 within reach- Helena · 92 km
- Belgrade · 115 km
- Bozeman · 127 km
- Missoula · 151 km
- Great Falls · 207 km
- Rexburg · 241 km
- Idaho Falls · 272 km
- Ammon · 275 km
Frost dates recorded at BUTTE BERT MOONEY AP, 14 km from the city center · 1991–2020 NOAA climate normals · zone from the USDA/PRISM 2023 map. How we compute this.
BlissGarden. "When to Plant in Butte-Silver Bow, MT — Frost Dates & Zone 5a." Frost normals: NOAA NCEI U.S. Climate Normals 1991–2020, station USW00024135. Retrieved from https://blissgarden.com/montana/butte-silver-bow.