Frost dates for Cohagen, 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
May 25
typical year
Safe to plant
June 9
frost is over in 9 of 10 years
First fall frost
September 14
typical year
Growing season
110 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 | – | Apr 27 – May 11 | – |
| Spinach | – | Apr 13 – May 4 | Jul 20 – Aug 3 |
| Lettuce | – | Apr 27 – May 18 | Jul 20 – Aug 3 |
| Radishes | – | Apr 27 – Jun 8 | Aug 3 – 17 |
| Onions | – | Apr 27 – May 11 | – |
| Potatoes | – | May 4 – 18 | – |
| Carrots | – | May 4 – 25 | Jun 22 – Jul 6 |
| Beets | – | Apr 27 – May 11 | Jul 6 – 20 |
| Kale | Mar 16 – 30 | Apr 27 – May 11 | Jul 6 – 20 |
| Broccoli | Mar 16 – 30 | May 11 – 25 | Jul 6 – 20 |
| Cabbage | Mar 2 – 16 | Apr 27 – May 11 | Jul 6 – 20 |
| Garlic | – | – | Aug 3 – 24 |
| Warm-season crops | |||
| Tomatoes | Apr 14 – 28 | Jun 9 – 23 | – |
| Peppers | Apr 7 – 21 | Jun 16 – 30 | – |
| Cucumbers | – | Jun 9 – 30 | – |
| Zucchini | – | Jun 9 – Jul 7 | – |
| Pumpkins | Season usually too short. Try a quick variety or row covers. | ||
| Green beans | – | Jun 9 – Jul 6 | – |
| Sweet corn | – | Jun 9 – Jul 7 | – |
| Basil | May 5 – 19 | Jun 16 – 23 | – |
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 | June 9 | May 25 | May 12 |
| Fall frost before | August 31 | September 14 | September 26 |
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 16 (May 29 in a late year), and the first one in fall around September 23.
Where these dates come from
NOAA weather station COHAGEN, MT US (USC00241875), 1991–2020 climate normals. It's the nearest station for 1 zip code, all within 3 miles:
59322
Planting dates follow common university extension advice; your local extension service can fine-tune them for your soil and microclimate.