Colorado planting calendar
Most of Colorado falls in USDA hardiness zones 3b–7a. Your exact zone depends on your local area — look it up by ZIP code — then open your zone's month-by-month calendar below.
USDA hardiness zones in Colorado
| Zone | Coldest temps | Avg. last spring frost |
|---|---|---|
| Zone 3b | -35 to -30°F | May 20 |
| Zone 4a | -30 to -25°F | May 15 |
| Zone 4b | -25 to -20°F | May 10 |
| Zone 5a | -20 to -15°F | May 5 |
| Zone 5b | -15 to -10°F | Apr 30 |
| Zone 6a | -10 to -5°F | Apr 21 |
| Zone 6b | -5 to 0°F | Apr 15 |
| Zone 7a | 0 to 5°F | Apr 7 |