In Colorado, the last spring frost usually comes between May 4 and June 14, and the first fall frost between September 10 and October 6, depending on where you live. Most of Colorado is in USDA hardiness zones 5a to 6b. In the highest mountain areas, frost is possible in any month.
Find the frost dates for your ZIP code
Frost dates from NOAA 1991–2020 U.S. Climate Normals, nearest weather station. Zones derived from the 2023 USDA Plant Hardiness Zone Map data (PRISM Climate Group, Oregon State University). This is not the official USDA Plant Hardiness Zone Map.
Frost dates for Colorado cities
Dates come from the NOAA weather station closest to each city. The last spring frost and first fall frost are the typical dates, with a 30% chance of frost after (or before) them. The safer planting date has only a 10% chance of a later spring frost: use it for tender plants like tomatoes, peppers and basil.
| City | Zone | Last frost | Safer date | First frost |
|---|---|---|---|---|
| Denver | 6a | May 4 | May 13 | Oct. 6 |
| Colorado Springs | 6a | May 8 | May 15 | Oct. 3 |
| Fort Collins | 5b | May 7 | May 14 | Oct. 2 |
| Pueblo | 6a | May 1 | May 8 | Oct. 7 |
| Longmont | 5b | May 13 | May 22 | Oct. 1 |
| Grand Junction | 7a | April 20 | April 28 | Oct. 18 |
| Castle Rock | 5b | May 15 | May 24 | Sep. 27 |
| Evans | 5b | May 7 | May 14 | Oct. 3 |
| Montrose | 6b | May 26 | June 4 | Sep. 25 |
| Durango | 6b | June 7 | June 15 | Sep. 22 |
Frost dates vary a lot across Colorado. Among the cities above, Grand Junction has the earliest last frost (around April 20) and Durango the latest (around June 7), about 7 weeks apart. Elevation, nearby water and local terrain all make a difference, so use the dates for the place closest to you, or look up your ZIP code.
Growing zones in Colorado
Most of Colorado is in USDA hardiness zones 5a to 6b. A typical frost-free growing season lasts about 157 days, longer in the warmest areas and shorter in the coldest.
Find planting dates for the main zones in Colorado:
- Zone 5 (about 51% of ZIP codes): Tomatoes, Peppers, Potatoes, Lettuce, Green beans, Cucumbers, Garlic, Tulips
- Zone 6 (about 45% of ZIP codes): Tomatoes, Peppers, Potatoes, Lettuce, Green beans, Cucumbers, Garlic, Tulips
See all crops in our planting guides, or build a planting calendar for your ZIP code.
How to use frost dates
- Cool-season crops such as peas, lettuce, spinach and onions can go in several weeks before your last spring frost.
- Warm-season crops such as tomatoes, peppers, squash and beans wait until after it, when the soil has warmed.
- Fall crops are timed back from your first fall frost, and garlic and tulips are planted around it.
- Frost dates are averages. Check the forecast before setting out tender plants.
Frequently asked questions
When is the last frost in Colorado?
It depends on where you live. Across most of Colorado, the last spring frost comes between May 4 and June 14. In Denver, it is around May 4.
When is the first frost in Colorado?
Across most of Colorado, the first fall frost comes between September 10 and October 6. In Denver, it is around October 6.
What planting zone is Colorado?
Most of Colorado is in USDA hardiness zones 5a to 6b. Enter your ZIP code above to find your exact zone.
When can I plant tomatoes in Colorado?
Plant tomatoes outside after your last frost, once nights stay above 50 °F. In Denver, the safer date, with only a 10% chance of a later frost, is around May 13. See when to plant tomatoes in zone 6.
Sources. Frost dates come from the nearest NOAA weather station to each city or ZIP code. Zones come from the 2023 USDA Plant Hardiness Zone Map ZIP code data. Our zone lookup is not the official USDA map.