Frost dates for Lewistown, 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 31
typical year
Safe to plant
June 18
frost is over in 9 of 10 years
First fall frost
September 14
typical year
Growing season
105 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 3 – 17 | – |
| Spinach | – | Apr 19 – May 10 | Jul 20 – Aug 3 |
| Lettuce | – | May 3 – 24 | Jul 20 – Aug 3 |
| Radishes | – | May 3 – Jun 14 | Aug 3 – 17 |
| Onions | – | May 3 – 17 | – |
| Potatoes | Season usually too short. Try a quick variety or row covers. | ||
| Carrots | – | May 10 – 31 | Jun 22 – Jul 6 |
| Beets | – | May 3 – 17 | Jul 6 – 20 |
| Kale | Mar 22 – Apr 5 | May 3 – 17 | Jul 6 – 20 |
| Broccoli | Mar 22 – Apr 5 | May 17 – 31 | Jul 6 – 20 |
| Cabbage | Mar 8 – 22 | May 3 – 17 | Jul 6 – 20 |
| Garlic | – | – | Aug 3 – 24 |
| Warm-season crops | |||
| Tomatoes | Apr 23 – May 7 | Jun 18 – Jul 2 | – |
| Peppers | Apr 16 – 30 | Jun 25 – Jul 9 | – |
| Cucumbers | – | Jun 18 – Jul 9 | – |
| Zucchini | – | Jun 18 – Jul 16 | – |
| Pumpkins | Season usually too short. Try a quick variety or row covers. | ||
| Green beans | – | Jun 18 – Jul 6 | – |
| Sweet corn | – | Jun 18 – Jul 16 | – |
| Basil | May 14 – 28 | Jun 25 – Jul 2 | – |
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 18 | May 31 | May 16 |
| Fall frost before | August 30 | September 14 | September 27 |
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 15 (May 29 in a late year), and the first one in fall around September 26.
Where these dates come from
NOAA weather station LEWISTOWN 11 SSE, MT US (USC00244978), 1991–2020 climate normals. It's the nearest station for 1 zip code, all within 10 miles:
59464
Planting dates follow common university extension advice; your local extension service can fine-tune them for your soil and microclimate.