USDA hardiness zones — 2023 map
Colorado hardiness zones — USDA planting zone map + what to grow
Zones 3b-7a · most of Colorado is zone 5b · West region
ColoradoUSDA zone range & map
On the 2023 USDA Plant Hardiness Zone Map, Colorado spans zones 3b-7a. The map shades the state from the high Rockies and mountain valleys (zone 3b-4b) through to the western slope around Grand Junction (zone 7a). The single most common half-zone across the populated state is zone 5b — that is the figure to use if you only remember one number for Colorado. Colorado gardening is shaped by altitude, intense sun, low humidity, and big day-night temperature swings. Frost can come in any month at high elevation.
| USDA zone range | Zones 3b-7a |
|---|---|
| Most common zone | Zone 5b |
| Coldest area | the high Rockies and mountain valleys (zone 3b-4b) |
| Warmest area | the western slope around Grand Junction (zone 7a) |
| Average last spring frost | mid-May |
| Average first fall frost | late September |
Source: USDA 2023 Plant Hardiness Zone Map (1991-2020 normals). Frost averages: NOAA/NCEI 1991-2020 climate normals. Local ZIP-level zones and frost dates can differ from these statewide figures.
Colorado hardiness zones by major city
Zones shift across Colorado with elevation and distance from the coast. Here is the 2023 USDA half-zone for the largest cities:
| City | USDA zone |
|---|---|
| Denver | Zone 6a |
| Colorado Springs | Zone 6a |
| Boulder | Zone 6a |
| Grand Junction | Zone 7a |
| Fort Collins | Zone 5b |
Need your exact zone? Run the ZIP-code zone finder for a precise half-zone and frost dates for your address.
ZIP-code zones in Colorado
Statewide ranges hide a lot. Tap your area for its exact USDA half-zone, last and first frost dates, and what to plant now:
- Arvada 80003 — Zone 6a
- Aurora (Central) 80012 — Zone 6a
- Aurora (Southeast) 80013 — Zone 6a
- Aurora (Smoky Hill) 80015 — Zone 5b
- Westminster 80031 — Zone 6a
- Littleton 80120 — Zone 6a
- Lakewood (South) 80123 — Zone 6a
- Highlands Ranch 80130 — Zone 5b
- Denver 80202 — Zone 6a
- Denver (Highlands) 80211 — Zone 6a
- Denver (Capitol Hill) 80218 — Zone 6a
- Denver (East) 80220 — Zone 6a
- Lakewood (Green Mountain) 80228 — Zone 6a
- Denver (Montbello) 80239 — Zone 6a
- Boulder 80302 — Zone 6a
- Longmont 80501 — Zone 5b
- Fort Collins 80521 — Zone 5b
- Fort Collins (South) 80525 — Zone 5b
- Greeley 80631 — Zone 5b
- Colorado Springs 80903 — Zone 6a
- Colorado Springs (Southeast) 80916 — Zone 6a
- Colorado Springs (North) 80918 — Zone 5b
- Pueblo 81001 — Zone 6b
- Grand Junction 81501 — Zone 7a
- Glenwood Springs 81601 — Zone 6a
What Colorado's zone range means for planting
Your hardiness zone tells you which perennials, shrubs, and trees will survive a typical Colorado winter, and it anchors when tender crops can go outside. Because Colorado spans 3b-7a, two gardeners in the same state can have very different planting calendars.
- Pick perennials hardy to your local zone. Across most of Colorado that means at least zone 5b; gardeners in the high Rockies and mountain valleys (zone 3b-4b) should choose hardier plants.
- Anchor tender crops to your frost dates. With a last spring frost around mid-May and first fall frost around late September, set out tomatoes, peppers, and basil after the last frost and protect them before the first.
- Adjust for your microclimate. Urban heat, a south-facing slope, or a cold valley pocket can shift your effective zone and frost dates by a half-zone or more from the statewide figure.
Find your exact zone in Colorado
The 3b-7a range is statewide. Growli pins your hardiness zone and frost dates to your exact ZIP code and sends a push notification before any forecast frost night for your saved location.
Frequently asked questions
What hardiness zone is Colorado?
Colorado spans USDA hardiness zones 3b-7a on the 2023 USDA Plant Hardiness Zone Map. The most common zone — covering the largest share of the populated state — is zone 5b. The coldest areas are the high Rockies and mountain valleys (zone 3b-4b) and the warmest are the western slope around Grand Junction (zone 7a).
When is the last frost in Colorado?
Across most of Colorado the average last spring frost falls around mid-May and the first fall frost around late September. These are statewide averages — colder, higher areas run later in spring and earlier in fall, so check a ZIP-level estimate for your exact spot.
What grows well in Colorado?
Colorado gardening is shaped by altitude, intense sun, low humidity, and big day-night temperature swings. Frost can come in any month at high elevation. Match plants to your local half-zone within the 3b-7a range: choose varieties hardy to at least zone 5b for reliable overwintering, and time tender crops around your local frost dates. The zone 5 planting guide lists vegetables, fruit, and ornamentals suited to most of the state.
Why does Colorado have more than one hardiness zone?
Hardiness zones track the average annual coldest temperature, which changes with latitude, elevation, distance from water, and urban heat. That is why Colorado ranges from the high Rockies and mountain valleys (zone 3b-4b) to the western slope around Grand Junction (zone 7a) — a span of 3b-7a — even though it is a single state.
Did Colorado's hardiness zone change in 2023?
The USDA updated the Plant Hardiness Zone Map in November 2023 using 1991-2020 climate data. About half the country, including parts of Colorado, shifted to the next warmer half-zone versus the 2012 map. The 3b-7a range here reflects the current 2023 map. Always confirm your address against the official USDA map for plant-survival decisions.