Frost dates for Swan Lake, 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 17
typical year
Safe to plant
June 4
frost is over in 9 of 10 years
First fall frost
September 19
typical year
Growing season
121 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 19 – May 3 | – |
| Spinach | – | Apr 5 – 26 | Jul 25 – Aug 8 |
| Lettuce | – | Apr 19 – May 10 | Jul 25 – Aug 8 |
| Radishes | – | Apr 19 – May 31 | Aug 8 – 22 |
| Onions | – | Apr 19 – May 3 | – |
| Potatoes | – | Apr 26 – May 10 | – |
| Carrots | – | Apr 26 – May 17 | Jun 27 – Jul 11 |
| Beets | – | Apr 19 – May 3 | Jul 11 – 25 |
| Kale | Mar 8 – 22 | Apr 19 – May 3 | Jul 11 – 25 |
| Broccoli | Mar 8 – 22 | May 3 – 17 | Jul 11 – 25 |
| Cabbage | Feb 22 – Mar 8 | Apr 19 – May 3 | Jul 11 – 25 |
| Garlic | – | – | Aug 8 – 29 |
| Warm-season crops | |||
| Tomatoes | Apr 9 – 23 | Jun 4 – 18 | – |
| Peppers | Apr 2 – 16 | Jun 11 – 25 | – |
| Cucumbers | – | Jun 4 – 25 | – |
| Zucchini | – | Jun 4 – Jul 2 | – |
| Pumpkins | – | Jun 4 – 25 | – |
| Green beans | – | Jun 4 – Jul 11 | – |
| Sweet corn | – | Jun 4 – Jul 2 | – |
| Basil | Apr 30 – May 14 | Jun 11 – 18 | – |
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 4 | May 17 | May 4 |
| Fall frost before | September 4 | September 19 | October 2 |
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 April 30 (May 13 in a late year), and the first one in fall around October 1.
Where these dates come from
NOAA weather station SWAN LAKE, MT US (USC00248087), 1991–2020 climate normals. It's the nearest station for 1 zip code, all within 4 miles:
59911
Planting dates follow common university extension advice; your local extension service can fine-tune them for your soil and microclimate.