USDA hardiness zone lookup
Casper, WY — USDA Zone 5a
Casper, Wyoming · 124-day growing season
Frost dates and growing season in Casper
| USDA hardiness zone | Zone 5a |
|---|---|
| Average last spring frost | May 18 |
| Average first fall frost | September 19 |
| Growing season length | ~124 days |
| Temperature range (F) | -20 to -10°F |
| Temperature range (C) | -29 to -23°C |
All of Casper's mapped ZIP codes fall in the same hardiness band, Zone 5a.
These are 50%-probability averages modeled from Casper's USDA hardiness zone and regional climate normals — not a single-station reading. In a typical year the last spring frost will have passed by May 18, but a colder-than-average year can run 1-2 weeks later. Plant tender crops (tomatoes, peppers, basil) once both soil and night temperatures are consistently warm — a thermometer beats the calendar.
Growing season in Casper
Casper, Wyoming sits in USDA Zone 5a, with roughly 124 frost-free days between an average last spring frost around May 18 and a first fall frost around September 19. That is a standard temperate season — most common vegetables finish comfortably, and a single main planting plus one succession round works well.
What grows in Casper
Casper falls in USDA Zone 5a, so the same hardiness constraints apply as the full Zone 5 guide. Vegetables, herbs, and fruit trees rated to Zone 5a (or hardier) will overwinter here in a typical year.
- Tomatoes (full range of varieties)
- Peppers
- Eggplant
- Squash, melons, cucumbers
- Beans (bush + pole)
- Sweet corn
- Apples, pears, plums
- Cherries (sweet + sour)
- Blueberries, raspberries
- Garlic
What to plant in Casper this week
Casper's last frost is around May 18. This is the spring transplant window — start tomatoes and peppers indoors if you haven't, and direct-sow cold-tolerant crops now.
- When to plant tomatoes in zone 5
- When to plant peppers in zone 5
- When to plant basil in zone 5
- When to plant bush beans in zone 5
- When to plant cucumbers in zone 5
Full planting calendar for Casper
Crop-by-crop sowing, transplant, and harvest dates calibrated to zone 5 averages:
- When to plant tomatoes in zone 5
- When to plant peppers in zone 5
- When to plant basil in zone 5
- When to plant garlic in zone 5
- When to plant lettuce in zone 5
- When to plant bush beans in zone 5
- When to plant cucumbers in zone 5
- When to plant summer squash in zone 5
- When to plant peas in zone 5
- When to plant carrots in zone 5
ZIP codes in Casper
Drill down to the precise frost window and planting calendar for a specific ZIP in Casper:
Local microclimate notes
Zone tables give you the average — but Caspergardens vary. South-facing walls and paved areas can run a full half-zone warmer than the published rating. Low-lying spots, frost pockets, and shaded north sides can run colder. If you've gardened here a few seasons, your own frost record — the last time you actually got frost damage — beats any national average.
Source and methodology
Hardiness zone from the USDA Plant Hardiness Zone Map (2023 revision). Frost-date and growing-season figures are modeled from Casper's USDA hardiness zone and regional NOAA 1991-2020 climate normals — zone-level estimates, not a per-station record, so treat them as planning guidance and confirm against your own local frost history. Crop recommendations draw on US Cooperative Extension references, curated by the Growli editorial team. Last reviewed June 2026.
Other cities in Wyoming
- Cheyenne, WY — USDA Zone 5b
- Cody, WY — USDA Zone 5a
- Evanston, WY — USDA Zone 4b
- Jackson, WY — USDA Zone 4a
- Laramie, WY — USDA Zone 4b
- Riverton, WY — USDA Zone 4b
- Sheridan, WY — USDA Zone 5a
- All of Wyoming by zone