Frost dates for Gibson Dam, MT
When the last spring frost and first fall frost usually come, and when to plant, from 30 years of NOAA weather records.
Last spring frost
June 12
typical year
Safe to plant
July 5
frost is over in 9 of 10 years
First fall frost
September 8
typical year
Growing season
88 days
frost-free, typical year
Frost watch this week
Tonight's and the next six nights' lows from the National Weather Service forecast for the station's location. Frost: 32°F or colder. Possible frost: 33–36°F, mostly in low spots on clear, still nights.
When to plant
Counted from this page's frost dates. Warm-season crops wait for the safe-to-plant date.
| Crop | Start indoors | Plant outside | Fall planting |
|---|---|---|---|
| Cool-season crops | |||
| Peas | – | May 15 – 29 | – |
| Spinach | – | May 1 – 22 | Jul 14 – 28 |
| Lettuce | – | May 15 – Jun 5 | Jul 14 – 28 |
| Radishes | – | May 15 – Jun 26 | Jul 28 – Aug 11 |
| Onions | – | May 15 – 29 | – |
| Potatoes | Season usually too short. Try a quick variety or row covers. | ||
| Carrots | – | May 22 – Jun 12 | Jun 16 – 30 |
| Beets | – | May 15 – 29 | Jun 30 – Jul 14 |
| Kale | Apr 3 – 17 | May 15 – 29 | Jun 30 – Jul 14 |
| Broccoli | Apr 3 – 17 | May 29 – Jun 12 | Jun 30 – Jul 14 |
| Cabbage | Mar 20 – Apr 3 | May 15 – 29 | Jun 30 – Jul 14 |
| Garlic | – | – | Jul 28 – Aug 18 |
| Warm-season crops | |||
| Tomatoes | Season usually too short. Try a quick variety or row covers. | ||
| Peppers | Season usually too short. Try a quick variety or row covers. | ||
| Cucumbers | – | Jul 5 – 26 | – |
| Zucchini | – | Jul 5 – Aug 2 | – |
| Pumpkins | Season usually too short. Try a quick variety or row covers. | ||
| Green beans | Season usually too short. Try a quick variety or row covers. | ||
| Sweet corn | Season usually too short. Try a quick variety or row covers. | ||
| Basil | May 31 – Jun 14 | Jul 12 – 19 | – |
Onions: from sets. Green beans: until 10 weeks before the first fall frost. Garlic: harvest next summer.
The year at a glance
Start indoors Plant outside Fall planting
The chance of frost, by date
| 1 year in 10 | Half of years | 9 years in 10 | |
|---|---|---|---|
| Spring frost after | July 5 | June 12 | May 25 |
| Fall frost before | August 23 | September 8 | September 24 |
Frost here means 32°F or colder. Read across: in 1 year in 10, spring frost carries on past the first date, which is why that date is the safe-to-plant date.
Hard freeze (28°F)
A hard freeze kills most garden plants, even hardy ones. The last one in spring usually comes around May 19 (June 5 in a late year), and the first one in fall around September 24.
Where these dates come from
NOAA weather station GIBSON DAM, MT US (USC00243489), 1991–2020 climate normals. It's the nearest station for 1 zip code, all within 8 miles:
59410
Planting dates follow common university extension advice; your local extension service can fine-tune them for your soil and microclimate.