Frost dates for Keystone, CO
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
June 6
typical year
Safe to plant
June 21
frost is over in 9 of 10 years
First fall frost
September 19
typical year
Growing season
103 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 | – | May 9 – 23 | – |
| Spinach | – | Apr 25 – May 16 | Jul 25 – Aug 8 |
| Lettuce | – | May 9 – 30 | Jul 25 – Aug 8 |
| Radishes | – | May 9 – Jun 20 | Aug 8 – 22 |
| Onions | – | May 9 – 23 | – |
| Potatoes | – | May 16 – 30 | – |
| Carrots | – | May 16 – Jun 6 | Jun 27 – Jul 11 |
| Beets | – | May 9 – 23 | Jul 11 – 25 |
| Kale | Mar 28 – Apr 11 | May 9 – 23 | Jul 11 – 25 |
| Broccoli | Mar 28 – Apr 11 | May 23 – Jun 6 | Jul 11 – 25 |
| Cabbage | Mar 14 – 28 | May 9 – 23 | Jul 11 – 25 |
| Garlic | – | – | Aug 8 – 29 |
| Warm-season crops | |||
| Tomatoes | Apr 26 – May 10 | Jun 21 – Jul 5 | – |
| Peppers | Apr 19 – May 3 | Jun 28 – Jul 12 | – |
| Cucumbers | – | Jun 21 – Jul 12 | – |
| Zucchini | – | Jun 21 – Jul 19 | – |
| Pumpkins | Season usually too short. Try a quick variety or row covers. | ||
| Green beans | – | Jun 21 – Jul 11 | – |
| Sweet corn | – | Jun 21 – Jul 19 | – |
| Basil | May 17 – 31 | Jun 28 – Jul 5 | – |
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 21 | June 6 | May 25 |
| Fall frost before | September 5 | September 19 | September 30 |
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 25 (June 9 in a late year), and the first one in fall around September 26.
Towns that use these dates
This is the nearest NOAA station with frost records for 2 towns.
Keystone, Montezuma
Where these dates come from
NOAA weather station CABIN CREEK, CO US (USC00051186), 1991–2020 climate normals. It's the nearest station for 3 zip codes, all within 13 miles:
80435, 80444, 80476
Planting dates follow common university extension advice; your local extension service can fine-tune them for your soil and microclimate.