Frost dates for Thermopolis, WY
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 24
typical year
Safe to plant
June 9
frost is over in 9 of 10 years
First fall frost
September 16
typical year
Growing season
112 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 26 – May 10 | – |
| Spinach | – | Apr 12 – May 3 | Jul 22 – Aug 5 |
| Lettuce | – | Apr 26 – May 17 | Jul 22 – Aug 5 |
| Radishes | – | Apr 26 – Jun 7 | Aug 5 – 19 |
| Onions | – | Apr 26 – May 10 | – |
| Potatoes | – | May 3 – 17 | – |
| Carrots | – | May 3 – 24 | Jun 24 – Jul 8 |
| Beets | – | Apr 26 – May 10 | Jul 8 – 22 |
| Kale | Mar 15 – 29 | Apr 26 – May 10 | Jul 8 – 22 |
| Broccoli | Mar 15 – 29 | May 10 – 24 | Jul 8 – 22 |
| Cabbage | Mar 1 – 15 | Apr 26 – May 10 | Jul 8 – 22 |
| Garlic | – | – | Aug 5 – 26 |
| Warm-season crops | |||
| Tomatoes | Apr 14 – 28 | Jun 9 – 23 | – |
| Peppers | Apr 7 – 21 | Jun 16 – 30 | – |
| Cucumbers | – | Jun 9 – 30 | – |
| Zucchini | – | Jun 9 – Jul 7 | – |
| Pumpkins | Season usually too short. Try a quick variety or row covers. | ||
| Green beans | – | Jun 9 – Jul 8 | – |
| Sweet corn | – | Jun 9 – Jul 7 | – |
| Basil | May 5 – 19 | Jun 16 – 23 | – |
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 9 | May 24 | May 12 |
| Fall frost before | September 4 | September 16 | September 29 |
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 11 (May 24 in a late year), and the first one in fall around September 24.
Towns that use these dates
This is the nearest NOAA station with frost records for 3 towns.
Thermopolis, East Thermopolis, Kirby
Where these dates come from
NOAA weather station THERMOPOLIS 9NE, WY US (USC00488884), 1991–2020 climate normals. It's the nearest station for 1 zip code, all within 4 miles:
82430
Planting dates follow common university extension advice; your local extension service can fine-tune them for your soil and microclimate.