Last frost date in Butte-Silver Bow, MT
Expect the last frost in Butte-Silver Bow around June 13. Frost after July 1 happens in only one year out of ten. The first fall frost usually arrives about September 5, which leaves 83 frost-free days. An early freeze before August 24 happens one year in ten.
- Safe after (10% risk)
- Jul 1
- Average first frost
- Sep 5
- Frost-free season
- 83 days
- Hard freeze (28°F) ends
- May 21
Hard freeze likely Fri night, low 27°F
National Weather Service forecast, updated Oct 22, 12:57 UTC
- ThuOct 2243°
- FriOct 2327°hard freeze
- SatOct 2428°hard freeze
- SunOct 2528°hard freeze
- MonOct 2629°frost
- TueOct 2728°hard freeze
- WedOct 2828°hard freeze
Planting calendar for Butte-Silver Bow
Windows count forward or back from the average frost dates above. Click a crop for dates across Montana.
TomatoesJun 20–Jul 4
PumpkinsJun 27–Jul 11
SunflowersJun 13–Jul 4
CucumbersJun 27–Jul 4
CornJun 20–Jul 4
Sweet potatoesJul 4–Jul 18
WatermelonJun 27–Jul 11
Green beansJun 20–Jul 11
ZucchiniJun 20–Jul 4
OkraJul 4–Jul 18
PeppersJun 27–Jul 11
BasilJun 20–Jul 4
Butternut squashJun 20–Jul 4
CantaloupeJun 27–Jul 11
EggplantJun 27–Jul 11
PotatoesMay 16–May 30
OnionsMay 2–May 23
CarrotsMay 23–Jun 27
LettuceMay 30–Jun 20
BroccoliMay 16–May 30
BeetsMay 16–Jun 27
PeasMay 2–May 16
CabbageMay 16–May 30
RadishesMay 9–Jun 20
Brussels sproutsMay 30–Jun 13
SpinachMay 2–May 23
CilantroMay 30–Jun 20
KaleMay 16–May 30
Collard greensMay 16–May 30
TurnipsMay 16–May 30
DillJun 13–Jun 27
CeleryJun 20–Jun 27
CauliflowerMay 30–Jun 13
LeeksMay 30–Jun 13
Swiss chardMay 30–Jun 27
ParsleyMay 30–Jun 20
Tulip bulbsAug 22–Sep 26
GarlicAug 15–Sep 19
Daffodil bulbsAug 8–Sep 19
StrawberriesMay 16–May 30
AsparagusMay 16–May 30The frost-free season here is short for tomatoes, pumpkins, sunflowers, cucumbers, corn, sweet potatoes, watermelon, peppers, basil, butternut squash, cantaloupe, eggplant. Start them indoors and look for early varieties.
Frost probabilities
| Threshold | Spring, 90% chance later | Spring, 50% | Spring, 10% | Fall, 10% chance earlier | Fall, 50% | Fall, 90% |
|---|---|---|---|---|---|---|
| Light frost, 32°F | May 27 | Jun 13 | Jul 1 | Aug 24 | Sep 5 | Sep 19 |
| Hard freeze, 28°F | May 8 | May 21 | Jun 10 | Sep 2 | Sep 17 | Oct 1 |
Read the spring 10% column as the date after which only one year in ten still gets frost. That is the safer date for tomatoes, peppers and basil.
Where these numbers come from
NOAA station Butte Bert Mooney Airport (USW00024135) sits 9.0 miles from the center of Butte-Silver Bow at 5,506 feet. Its averages cover 1991 to 2020. Low spots, valleys and open fields can keep getting frost a week or two after the station stops; city centers and lakeshores usually get less of it.
Questions
When is the last frost in Butte-Silver Bow, MT?
The average last frost date in Butte-Silver Bow is June 13, based on NOAA 1991–2020 climate normals. There is a 10% chance of frost after July 1.
When is the first frost in Butte-Silver Bow?
The first frost in fall usually comes around September 5. One year in ten it arrives before August 24.
How long is the growing season in Butte-Silver Bow?
About 83 days between the average last and first frost.
When should I plant tomatoes in Butte-Silver Bow?
Plant tomato seedlings outside from June 20 to July 4. Start seeds indoors six to eight weeks earlier.