Frost dates for Three Forks, 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 9
typical year
Safe to plant
May 24
frost is over in 9 of 10 years
First fall frost
September 27
typical year
Growing season
139 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 11 – 25 | – |
| Spinach | – | Mar 28 – Apr 18 | Aug 2 – 16 |
| Lettuce | – | Apr 11 – May 2 | Aug 2 – 16 |
| Radishes | – | Apr 11 – May 23 | Aug 16 – 30 |
| Onions | – | Apr 11 – 25 | – |
| Potatoes | – | Apr 18 – May 2 | – |
| Carrots | – | Apr 18 – May 9 | Jul 5 – 19 |
| Beets | – | Apr 11 – 25 | Jul 19 – Aug 2 |
| Kale | Feb 28 – Mar 14 | Apr 11 – 25 | Jul 19 – Aug 2 |
| Broccoli | Feb 28 – Mar 14 | Apr 25 – May 9 | Jul 19 – Aug 2 |
| Cabbage | Feb 14 – 28 | Apr 11 – 25 | Jul 19 – Aug 2 |
| Garlic | – | – | Aug 16 – Sep 6 |
| Warm-season crops | |||
| Tomatoes | Mar 29 – Apr 12 | May 24 – Jun 7 | – |
| Peppers | Mar 22 – Apr 5 | May 31 – Jun 14 | – |
| Cucumbers | – | May 24 – Jun 14 | – |
| Zucchini | – | May 24 – Jun 21 | – |
| Pumpkins | – | May 24 – Jun 14 | – |
| Green beans | – | May 24 – Jul 19 | – |
| Sweet corn | – | May 24 – Jun 21 | – |
| Basil | Apr 19 – May 3 | May 31 – Jun 7 | – |
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 | May 24 | May 9 | April 29 |
| Fall frost before | September 12 | September 27 | October 9 |
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 29 (May 10 in a late year), and the first one in fall around October 6.
Towns that use these dates
This is the nearest NOAA station with frost records for 1 town.
Three Forks
Where these dates come from
NOAA weather station TRIDENT, MT US (USC00248363), 1991–2020 climate normals. It's the nearest station for 2 zip codes, all within 20 miles:
59721, 59752
Planting dates follow common university extension advice; your local extension service can fine-tune them for your soil and microclimate.