Frost dates for Harlem, 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 16
typical year
Safe to plant
May 31
frost is over in 9 of 10 years
First fall frost
September 21
typical year
Growing season
125 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 18 – May 2 | – |
| Spinach | – | Apr 4 – 25 | Jul 27 – Aug 10 |
| Lettuce | – | Apr 18 – May 9 | Jul 27 – Aug 10 |
| Radishes | – | Apr 18 – May 30 | Aug 10 – 24 |
| Onions | – | Apr 18 – May 2 | – |
| Potatoes | – | Apr 25 – May 9 | – |
| Carrots | – | Apr 25 – May 16 | Jun 29 – Jul 13 |
| Beets | – | Apr 18 – May 2 | Jul 13 – 27 |
| Kale | Mar 7 – 21 | Apr 18 – May 2 | Jul 13 – 27 |
| Broccoli | Mar 7 – 21 | May 2 – 16 | Jul 13 – 27 |
| Cabbage | Feb 21 – Mar 7 | Apr 18 – May 2 | Jul 13 – 27 |
| Garlic | – | – | Aug 10 – 31 |
| Warm-season crops | |||
| Tomatoes | Apr 5 – 19 | May 31 – Jun 14 | – |
| Peppers | Mar 29 – Apr 12 | Jun 7 – 21 | – |
| Cucumbers | – | May 31 – Jun 21 | – |
| Zucchini | – | May 31 – Jun 28 | – |
| Pumpkins | – | May 31 – Jun 21 | – |
| Green beans | – | May 31 – Jul 13 | – |
| Sweet corn | – | May 31 – Jun 28 | – |
| Basil | Apr 26 – May 10 | Jun 7 – 14 | – |
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 31 | May 16 | May 4 |
| Fall frost before | September 8 | September 21 | October 2 |
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 6 (May 20 in a late year), and the first one in fall around September 29.
Towns that use these dates
This is the nearest NOAA station with frost records for 1 town.
Harlem
Where these dates come from
NOAA weather station HARLEM, MT US (USC00243929), 1991–2020 climate normals. It's the nearest station for 1 zip code, all within 19 miles:
59529
Planting dates follow common university extension advice; your local extension service can fine-tune them for your soil and microclimate.