What Planting Zones Are in Wyoming?
Wyoming spans USDA hardiness zones 4a to 5b, where the average coldest winter night ranges from −30 °F to −10 °F (−34.4 °C to −23.3 °C). Zone 5a covers the most ZIP codes, 58%, and zones 4b to 5b together cover 95% of the state.
Bars show each zone's share of the 191 Wyoming ZIP codes in the official 2023 USDA ZIP code table; select a zone for its temperatures and hardy plants.
What Hardiness Zone Are Wyoming Cities In?
Cheyenne is in zone 5b, Casper is in zone 5a, Gillette is in zone 4b and Laramie is in zone 4a. The table lists the zone, winter low and average frost dates for 18 Wyoming cities, using the ZIP code nearest each city center.
| City | ZIP | Zone | Winter low | Last frost | First frost |
|---|---|---|---|---|---|
| Cheyenne | 82005 | 5b | −15 °F to −10 °F | May 14 | Oct 1 |
| Casper | 82644 | 5a | −20 °F to −15 °F | May 10 | Sep 29 |
| Gillette | 82727 | 4b | −25 °F to −20 °F | May 15 | Oct 1 |
| Laramie | 82072 | 4a | −30 °F to −25 °F | Jun 7 | Sep 4 |
| Rock Springs | 82943 | 5a | −20 °F to −15 °F | May 24 | Sep 24 |
| Sheridan | 82801 | 5a | −20 °F to −15 °F | May 18 | Sep 24 |
| Evanston | 82933 | 5b | −15 °F to −10 °F | Jun 14 | Sep 9 |
| Green River | 82935 | 5a | −20 °F to −15 °F | May 24 | Sep 22 |
| Riverton | 82501 | 5a | −20 °F to −15 °F | May 12 | Sep 24 |
| Jackson | 83001 | 4b | −25 °F to −20 °F | Jun 20 | Aug 31 |
| Cody | 82440 | 5a | −20 °F to −15 °F | May 15 | Sep 25 |
| Rawlins | 82334 | 5a | −20 °F to −15 °F | May 12 | Oct 4 |
| Lander | 82515 | 5a | −20 °F to −15 °F | May 18 | Sep 27 |
| Powell | 82440 | 5a | −20 °F to −15 °F | May 15 | Sep 25 |
| Douglas | 82633 | 5a | −20 °F to −15 °F | May 23 | Sep 22 |
| Torrington | 82240 | 5a | −20 °F to −15 °F | May 11 | Sep 29 |
| Worland | 82401 | 4b | −25 °F to −20 °F | May 4 | Oct 1 |
| Buffalo | 82834 | 5a | −20 °F to −15 °F | May 24 | Sep 21 |
Zone: 2023 USDA ZIP code table for the ZIP code nearest each city's Census center point. Frost dates: 50% (median) dates from the nearest NOAA station, 1991–2020 normals. Cities: the largest Wyoming places by 2024 Census population estimates, spread across the state, plus the largest place in each common zone. Large cities can span two half zones.
Which Parts of Wyoming Are in Each Zone?
Zone 4a, the coldest Wyoming zone, covers 5% of ZIP codes around Laramie. Zone 5b, the warmest, covers 15% around Cheyenne, Evanston and Afton. The table lists the largest places in every zone.
| Zone | Avg. coldest night | Share of ZIPs | Largest places in this zone |
|---|---|---|---|
| Zone 4a | −30 °F to −25 °F | 5% (10) | Laramie |
| Zone 4b | −25 °F to −20 °F | 23% (43) | Gillette, Jackson, Worland, Newcastle |
| Zone 5a | −20 °F to −15 °F | 58% (110) | Casper, Rock Springs, Sheridan, Green River |
| Zone 5b | −15 °F to −10 °F | 15% (28) | Cheyenne, Evanston, Afton, Star Valley Ranch |
Places: incorporated places with 1,000+ residents, assigned the zone of the ZIP code nearest their Census center point.
What Do the Hardiness Zones Mean for Wyoming Gardeners?
A Wyoming gardener in zone 5b sees winter lows about 15 °F milder than one in zone 4a, so a shrub or perennial that thrives in one part of the state can die in another. Choose plants rated to your own ZIP code's zone or colder.
Hardiness zones follow latitude, elevation and large bodies of water rather than state lines. Higher ground and inland valleys that trap cold air usually sit in colder half zones, while cities, coasts and large lakes moderate winter lows. Within Wyoming, a plant labelled “zones 4–5” survives winter in at least 95% of ZIP codes, but plants at the edge of their range benefit from mulch and a sheltered spot. Enter a ZIP code in the USDA hardiness zone finder by ZIP code to check your exact half zone before buying perennials.
A zone describes winter cold only. Summer heat, humidity, rainfall and soil decide whether a cold-hardy plant thrives, and planting dates for vegetables follow frost dates, not zones: two Wyoming towns in the same zone can have last frosts weeks apart.
What Plants Grow Well Across Wyoming?
154 plants in PlantoScan's catalogue are hardy in every zone from 4b to 5b, the zones that cover 95% of Wyoming ZIP codes. Popular examples include peony, daisy and poppy.
Peony
Paeonia lactiflora
Zone 3 – 8
AI generated
- DaisyBellis perennisPlantoScan
Daisy
Bellis perennis
Zone 4a – 8b
Poppy
Papaver somniferum
Zone 3a – 9b
AI generated
Daffodil
Narcissus poeticus
Zone 3 – 8
AI generated
Alfalfa
Medicago sativa
Zone 3a – 10a
AI generated
Hyacinth
Hyacinthus orientalis
Zone 4 – 8
AI generated
Tiger Lily
Lilium lancifolium
Zone 3 – 8
AI generated
Forget Me Not
Myosotis sylvatica
Zone 3 – 8
AI generated
Lemon Balm
Melissa officinalis
Zone 4a – 9b
Image: PlantoScan
Hardiness ranges come from PlantoScan's plant database; gardeners in Wyoming's colder or warmer edge zones should check each plant's full range.
When Is the Last Frost in Wyoming?
Across most Wyoming ZIP codes, the average last spring frost falls between May 12 and June 14, from May 4 in Worland to June 20 in Jackson. Tender vegetables such as tomatoes go out 1 to 2 weeks after the local date.
The last and first frost dates for Wyoming cities include the safer 90% planting date, the fall frost date, growing season length and a tomato planting table for each city.
Frequently Asked Questions
- What planting zone is Wyoming?
- Wyoming spans USDA hardiness zones 4a to 5b on the 2023 USDA Plant Hardiness Zone Map. Zone 5a is the most common, covering 58% of the state's 191 ZIP codes, and zones 4b to 5b together cover 95%.
- What hardiness zone is Cheyenne, Wyoming?
- Cheyenne is in USDA hardiness zone 5b (ZIP 82005), where the average coldest winter night reaches −15 °F to −10 °F. Its average last spring frost is May 14 and its first fall frost October 1.
- What hardiness zone is Casper, Wyoming?
- Casper is in USDA hardiness zone 5a (ZIP 82644), where the average coldest winter night reaches −20 °F to −15 °F. Its average last spring frost is May 10 and its first fall frost September 29.
- What hardiness zone is Gillette, Wyoming?
- Gillette is in USDA hardiness zone 4b (ZIP 82727), where the average coldest winter night reaches −25 °F to −20 °F. Its average last spring frost is May 15 and its first fall frost October 1.
- What is the coldest hardiness zone in Wyoming?
- Zone 4a (−30 °F to −25 °F) is the coldest zone in Wyoming, found in 10 ZIP codes around Laramie. The warmest is zone 5b (−15 °F to −10 °F), around Cheyenne and Evanston.
Zones: 2023 USDA Plant Hardiness Zone Map ZIP code table, USDA Agricultural Research Service and the PRISM Climate Group, Oregon State University, used without changes. Frost dates: NOAA National Centers for Environmental Information, 1991–2020 U.S. Climate Normals. City locations and populations: U.S. Census Bureau Gazetteer files and Vintage 2024 population estimates. PlantoScan is not affiliated with or endorsed by these agencies.