Frost dates for Port Of Morgan, 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 19
typical year
Safe to plant
June 2
frost is over in 9 of 10 years
First fall frost
September 22
typical year
Growing season
124 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 21 – May 5 | – |
| Spinach | – | Apr 7 – 28 | Jul 28 – Aug 11 |
| Lettuce | – | Apr 21 – May 12 | Jul 28 – Aug 11 |
| Radishes | – | Apr 21 – Jun 2 | Aug 11 – 25 |
| Onions | – | Apr 21 – May 5 | – |
| Potatoes | – | Apr 28 – May 12 | – |
| Carrots | – | Apr 28 – May 19 | Jun 30 – Jul 14 |
| Beets | – | Apr 21 – May 5 | Jul 14 – 28 |
| Kale | Mar 10 – 24 | Apr 21 – May 5 | Jul 14 – 28 |
| Broccoli | Mar 10 – 24 | May 5 – 19 | Jul 14 – 28 |
| Cabbage | Feb 24 – Mar 10 | Apr 21 – May 5 | Jul 14 – 28 |
| Garlic | – | – | Aug 11 – Sep 1 |
| Warm-season crops | |||
| Tomatoes | Apr 7 – 21 | Jun 2 – 16 | – |
| Peppers | Mar 31 – Apr 14 | Jun 9 – 23 | – |
| Cucumbers | – | Jun 2 – 23 | – |
| Zucchini | – | Jun 2 – 30 | – |
| Pumpkins | – | Jun 2 – 23 | – |
| Green beans | – | Jun 2 – Jul 14 | – |
| Sweet corn | – | Jun 2 – 30 | – |
| Basil | Apr 28 – May 12 | Jun 9 – 16 | – |
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 2 | May 19 | May 5 |
| Fall frost before | September 9 | 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 8 (May 21 in a late year), and the first one in fall around September 30.
Where these dates come from
NOAA weather station PORT OF MORGAN, MT US (USC00246672), 1991–2020 climate normals. It's the nearest station for 2 zip codes, all within 18 miles:
59537, 59544
Planting dates follow common university extension advice; your local extension service can fine-tune them for your soil and microclimate.