Frost dates for Sidney, 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 11
typical year
Safe to plant
May 25
frost is over in 9 of 10 years
First fall frost
September 27
typical year
Growing season
137 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 13 – 27 | – |
| Spinach | – | Mar 30 – Apr 20 | Aug 2 – 16 |
| Lettuce | – | Apr 13 – May 4 | Aug 2 – 16 |
| Radishes | – | Apr 13 – May 25 | Aug 16 – 30 |
| Onions | – | Apr 13 – 27 | – |
| Potatoes | – | Apr 20 – May 4 | – |
| Carrots | – | Apr 20 – May 11 | Jul 5 – 19 |
| Beets | – | Apr 13 – 27 | Jul 19 – Aug 2 |
| Kale | Mar 2 – 16 | Apr 13 – 27 | Jul 19 – Aug 2 |
| Broccoli | Mar 2 – 16 | Apr 27 – May 11 | Jul 19 – Aug 2 |
| Cabbage | Feb 16 – Mar 2 | Apr 13 – 27 | Jul 19 – Aug 2 |
| Garlic | – | – | Aug 16 – Sep 6 |
| Warm-season crops | |||
| Tomatoes | Mar 30 – Apr 13 | May 25 – Jun 8 | – |
| Peppers | Mar 23 – Apr 6 | Jun 1 – 15 | – |
| Cucumbers | – | May 25 – Jun 15 | – |
| Zucchini | – | May 25 – Jun 22 | – |
| Pumpkins | – | May 25 – Jun 15 | – |
| Green beans | – | May 25 – Jul 19 | – |
| Sweet corn | – | May 25 – Jun 22 | – |
| Basil | Apr 20 – May 4 | Jun 1 – 8 | – |
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 25 | May 11 | April 30 |
| Fall frost before | September 13 | 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 May 2 (May 16 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 2 towns.
Sidney, Fairview
Where these dates come from
NOAA weather station SIDNEY, MT US (USC00247560), 1991–2020 climate normals. It's the nearest station for 4 zip codes, all within 25 miles:
58838, 59221, 59243, 59270
Planting dates follow common university extension advice; your local extension service can fine-tune them for your soil and microclimate.