Frost dates for Harlowton, 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 23
typical year
Safe to plant
June 6
frost is over in 9 of 10 years
First fall frost
September 16
typical year
Growing season
113 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 25 – May 9 | – |
| Spinach | – | Apr 11 – May 2 | Jul 22 – Aug 5 |
| Lettuce | – | Apr 25 – May 16 | Jul 22 – Aug 5 |
| Radishes | – | Apr 25 – Jun 6 | Aug 5 – 19 |
| Onions | – | Apr 25 – May 9 | – |
| Potatoes | – | May 2 – 16 | – |
| Carrots | – | May 2 – 23 | Jun 24 – Jul 8 |
| Beets | – | Apr 25 – May 9 | Jul 8 – 22 |
| Kale | Mar 14 – 28 | Apr 25 – May 9 | Jul 8 – 22 |
| Broccoli | Mar 14 – 28 | May 9 – 23 | Jul 8 – 22 |
| Cabbage | Feb 28 – Mar 14 | Apr 25 – May 9 | Jul 8 – 22 |
| Garlic | – | – | Aug 5 – 26 |
| Warm-season crops | |||
| Tomatoes | Apr 11 – 25 | Jun 6 – 20 | – |
| Peppers | Apr 4 – 18 | Jun 13 – 27 | – |
| Cucumbers | – | Jun 6 – 27 | – |
| Zucchini | – | Jun 6 – Jul 4 | – |
| Pumpkins | – | Jun 6 – 27 | – |
| Green beans | – | Jun 6 – Jul 8 | – |
| Sweet corn | – | Jun 6 – Jul 4 | – |
| Basil | May 2 – 16 | Jun 13 – 20 | – |
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 6 | May 23 | May 12 |
| Fall frost before | September 1 | September 16 | September 28 |
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 12 (May 23 in a late year), and the first one in fall around September 27.
Towns that use these dates
This is the nearest NOAA station with frost records for 1 town.
Harlowton
Where these dates come from
NOAA weather station HARLOWTON, MT US (USC00243939), 1991–2020 climate normals. It's the nearest station for 1 zip code, all within 3 miles:
59036
Planting dates follow common university extension advice; your local extension service can fine-tune them for your soil and microclimate.