Frost dates for Fort Benton, 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 15
typical year
Safe to plant
May 30
frost is over in 9 of 10 years
First fall frost
September 22
typical year
Growing season
129 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 17 – May 1 | – |
| Spinach | – | Apr 3 – 24 | Jul 28 – Aug 11 |
| Lettuce | – | Apr 17 – May 8 | Jul 28 – Aug 11 |
| Radishes | – | Apr 17 – May 29 | Aug 11 – 25 |
| Onions | – | Apr 17 – May 1 | – |
| Potatoes | – | Apr 24 – May 8 | – |
| Carrots | – | Apr 24 – May 15 | Jun 30 – Jul 14 |
| Beets | – | Apr 17 – May 1 | Jul 14 – 28 |
| Kale | Mar 6 – 20 | Apr 17 – May 1 | Jul 14 – 28 |
| Broccoli | Mar 6 – 20 | May 1 – 15 | Jul 14 – 28 |
| Cabbage | Feb 20 – Mar 6 | Apr 17 – May 1 | Jul 14 – 28 |
| Garlic | – | – | Aug 11 – Sep 1 |
| Warm-season crops | |||
| Tomatoes | Apr 4 – 18 | May 30 – Jun 13 | – |
| Peppers | Mar 28 – Apr 11 | Jun 6 – 20 | – |
| Cucumbers | – | May 30 – Jun 20 | – |
| Zucchini | – | May 30 – Jun 27 | – |
| Pumpkins | – | May 30 – Jun 20 | – |
| Green beans | – | May 30 – Jul 14 | – |
| Sweet corn | – | May 30 – Jun 27 | – |
| Basil | Apr 25 – May 9 | Jun 6 – 13 | – |
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 30 | May 15 | May 3 |
| Fall frost before | September 7 | September 22 | October 4 |
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 4 (May 14 in a late year), and the first one in fall around October 1.
Towns that use these dates
This is the nearest NOAA station with frost records for 1 town.
Fort Benton
Where these dates come from
NOAA weather station FT BENTON, MT US (USC00243113), 1991–2020 climate normals. It's the nearest station for 1 zip code, all within 7 miles:
59442
Planting dates follow common university extension advice; your local extension service can fine-tune them for your soil and microclimate.