Frost Dates for Casper, WY 82601
Last spring frost May 22 · First fall frost September 19 · 120 frost-free days · USDA Zone 5a
ZIP 82601 has about 26,700 people, one of 3 ZIP codes in Casper.
Moderate season: 120 frost-free days. Spring frost risk spans May 5–June 8 (34 days). Fall frost risk spans September 10–September 30 (20 days).
Frost probability for 82601
| Frost | 10% | 50% | 90% |
|---|---|---|---|
| Spring (last frost) | June 8 | May 22 | May 5 |
| Fall (first frost) | September 10 | September 19 | September 30 |
Dates come from NOAA 1971–2000 freeze probabilities at CASPER-NATRONA CO AP (21.3 km away); the 50% date is the median year.
Which crops fit a 120-day season in Casper
In Casper (120 frost-free days, a moderate season), 34 of 56 planner crops fit outright, 15 get two plantings, 6 need an indoor start, 1 crop is perennial.
| Crop | Start indoors | Plant out / sow | Days you have | Verdict | Last sow date |
|---|---|---|---|---|---|
| Tomato | Apr 17 | Jun 5–Jun 12 | 78 | head-start: Even planted out Jun 5, the outdoor season is about 2 days short; choose an early variety or grow under cover. | — |
| Pepper | Apr 10 | Jun 5–Jun 12 | 78 | fits: 75 days to maturity, 78 available after Jun 5. | — |
| Lettuce | Mar 27 | Apr 24–May 1 | 155 | two-plantings: Plant Apr 24 and again by Jul 29; both mature before Sep 26. | Jul 29 |
| Carrots | — | May 1–May 8 | 162 | fits: 70 days to maturity, 162 available after May 1. | Jul 18 |
| Cucumber | May 1 | Jun 5–Jun 12 | 92 | fits: 60 days to maturity, 92 available after Jun 5. | Jun 23 |
| Beans | — | May 29–Jun 12 | 106 | fits: 60 days to maturity, 106 available after May 29. | Jun 30 |
| Peas | — | Mar 27–Jun 5 | 183 | fits: 65 days to maturity, 183 available after Mar 27. | Jul 9 |
| Zucchini | May 8 | Jun 5–Jun 12 | 92 | fits: 55 days to maturity, 92 available after Jun 5. | Jun 28 |
| Onion | Feb 27 | Apr 24–May 8 | 155 | fits: 100 days to maturity, 155 available after Apr 24. | — |
| Spinach | — | Mar 27–May 15 | 197 | two-plantings: Plant Mar 27 and again by Aug 17; both mature before Oct 10. | Aug 17 |
| Kale | Mar 13 | Apr 24–May 8 | 169 | two-plantings: Plant Apr 24 and again by Aug 2; both mature before Oct 10. | Aug 2 |
| Broccoli | Mar 27 | Apr 24–May 8 | 155 | fits: 80 days to maturity, 155 available after Apr 24. | Jun 24 |
| Cabbage | Mar 27 | Apr 24–May 8 | 169 | fits: 70 days to maturity, 169 available after Apr 24. | Jul 18 |
| Radish | — | Mar 27–Jun 19 | 183 | two-plantings: Plant Mar 27 and again by Aug 18; both mature before Sep 26. | Aug 18 |
| Beets | — | Mar 27–Jun 19 | 183 | two-plantings: Plant Mar 27 and again by Jul 19; both mature before Sep 26. | Jul 19 |
| Potatoes | — | May 8–May 15 | 141 | fits: 90 days to maturity, 141 available after May 8. | — |
| Garlic | — | Sep 19 | 225 | overwinter: Plant Sep 19 to Oct 10; harvest the following summer. | Oct 10 |
| Strawberry | — | Apr 17–Jun 12 | 176 | perennial: A perennial: plant Apr 17; it fruits from the following year and keeps producing for several years. | — |
| Corn | Apr 24 | May 29–Jun 5 | 92 | fits: 75 days to maturity, 92 available after May 29. | Jun 1 |
| Pumpkin | May 8 | Jun 5–Jun 5 | 85 | head-start: Even planted out Jun 5, the outdoor season is about 15 days short; choose an early variety or grow under cover. | — |
| Cauliflower | Apr 10 | May 15–May 29 | 134 | fits: 75 days to maturity, 134 available after May 15. | Jun 29 |
| Swiss Chard | Mar 27 | May 8–May 8 | 141 | two-plantings: Plant May 8 and again by Jul 19; both mature before Sep 26. | Jul 19 |
| Arugula | — | Mar 27–Jun 19 | 197 | two-plantings: Plant Mar 27 and again by Aug 17; both mature before Oct 10. | Aug 17 |
| Brussel Sprouts | Mar 27 | Apr 24–May 8 | 169 | fits: 100 days to maturity, 169 available after Apr 24. | Jun 18 |
| Butternut Squash | May 8 | Jun 5–Jun 12 | 85 | head-start: Even planted out Jun 5, the outdoor season is about 15 days short; choose an early variety or grow under cover. | — |
| Eggplant | Apr 3 | Jun 5–Jun 12 | 78 | fits: 70 days to maturity, 78 available after Jun 5. | — |
| Okra | Apr 24 | May 29–Jun 5 | 99 | fits: 55 days to maturity, 99 available after May 29. | Jun 28 |
| Basil | Apr 17 | Jun 12–Jun 12 | 85 | fits: 60 days to maturity, 85 available after Jun 12. | Jun 23 |
| Cilantro | — | Apr 24–May 15 | 155 | two-plantings: Plant Apr 24 and again by Jul 24; both mature before Sep 26. | Jul 24 |
| Parsley | Mar 13 | May 29–Jun 5 | 120 | fits: 70 days to maturity, 120 available after May 29. | Jul 4 |
| Celery | Mar 13 | May 29–Jun 12 | 120 | fits: 120 days to maturity, 120 available after May 29. | — |
| Scallions | Mar 13 | Apr 24–May 8 | 169 | two-plantings: Plant Apr 24 and again by Jul 28; both mature before Oct 10. | Jul 28 |
| Turnip | — | Apr 24–May 8 | 169 | two-plantings: Plant Apr 24 and again by Aug 7; both mature before Oct 10. | Aug 7 |
| Kohlrabi | — | Apr 10–Apr 24 | 183 | two-plantings: Plant Apr 10 and again by Aug 2; both mature before Oct 10. | Aug 2 |
| Bok Choy | Apr 24 | May 15–May 22 | 134 | two-plantings: Plant May 15 and again by Jul 29; both mature before Sep 26. | Jul 29 |
| Collards | Mar 13 | Apr 24–May 8 | 169 | two-plantings: Plant Apr 24 and again by Jul 28; both mature before Oct 10. | Jul 28 |
| Cantaloupe | May 8 | Jun 5–Jun 12 | 78 | head-start: Even planted out Jun 5, the outdoor season is about 7 days short; choose an early variety or grow under cover. | — |
| Chives | Feb 27 | May 29–Jun 5 | 134 | fits: 90 days to maturity, 134 available after May 29. | — |
| Dill | — | Mar 27–Jun 19 | 183 | two-plantings: Plant Mar 27 and again by Jul 19; both mature before Sep 26. | Jul 19 |
| Oregano | Mar 13 | May 29–Jun 5 | 134 | fits: 80 days to maturity, 134 available after May 29. | — |
| Rosemary | Feb 27 | May 29–Jun 5 | 120 | fits: 80 days to maturity, 120 available after May 29. | — |
| Sage | Mar 27 | May 29–Jun 5 | 134 | fits: 75 days to maturity, 134 available after May 29. | — |
| Thyme | Mar 13 | May 29–Jun 5 | 134 | fits: 90 days to maturity, 134 available after May 29. | — |
| Calendula | Apr 10 | May 8–May 22 | 141 | two-plantings: Plant May 8 and again by Jul 24; both mature before Sep 26. | Jul 24 |
| Cosmos | Apr 24 | May 22–Jun 5 | 106 | fits: 60 days to maturity, 106 available after May 22. | Jun 23 |
| Lavender | Feb 27 | May 22–Jun 5 | 141 | fits: 90 days to maturity, 141 available after May 22. | — |
| Marigolds | Apr 10 | May 22–May 29 | 106 | fits: 50 days to maturity, 106 available after May 22. | Jul 3 |
| Melons | May 8 | Jun 5–Jun 12 | 78 | head-start: Even planted out Jun 5, the outdoor season is about 7 days short; choose an early variety or grow under cover. | — |
| Mint | — | May 22–Jun 5 | 141 | fits: 90 days to maturity, 141 available after May 22. | — |
| Nasturtiums | Apr 24 | May 22–May 29 | 106 | fits: 55 days to maturity, 106 available after May 22. | Jun 28 |
| Pole Beans | — | May 29–Jun 12 | 99 | fits: 65 days to maturity, 99 available after May 29. | Jun 18 |
| Spaghetti Squash | May 8 | Jun 5–Jun 12 | 85 | head-start: Even planted out Jun 5, the outdoor season is about 5 days short; choose an early variety or grow under cover. | — |
| Sunflowers | — | May 22–Jun 5 | 106 | fits: 70 days to maturity, 106 available after May 22. | Jun 13 |
| Tomatillos | Mar 27 | May 29–Jun 5 | 85 | fits: 75 days to maturity, 85 available after May 29. | — |
| Watermelon | May 8 | May 29–Jun 5 | 85 | fits: 80 days to maturity, 85 available after May 29. | — |
| Yellow Squash | May 8 | Jun 5–Jun 12 | 92 | fits: 55 days to maturity, 92 available after Jun 5. | Jun 28 |
| Zinnias | Apr 24 | May 22–Jun 5 | 106 | fits: 60 days to maturity, 106 available after May 22. | Jun 23 |
Month by month in Casper
| Month | What to do |
|---|---|
| January | Plan your garden layout and order seeds. Research varieties suited to your frost dates. |
| February | Start indoors: Chives (Feb 27), Lavender (Feb 27), Onion (Feb 27), Rosemary (Feb 27). |
| March | Start indoors: Celery (Mar 13), Collards (Mar 13), Kale (Mar 13), Oregano (Mar 13), Parsley (Mar 13), Scallions (Mar 13), +8 more. Direct sow from: Arugula (Mar 27), Beets (Mar 27), Dill (Mar 27), Peas (Mar 27), Radish (Mar 27), Spinach (Mar 27). |
| April | Start indoors: Eggplant (Apr 3), Calendula (Apr 10), Cauliflower (Apr 10), Marigolds (Apr 10), Pepper (Apr 10), Basil (Apr 17), +7 more. Direct sow from: Kohlrabi (Apr 10), Cilantro (Apr 24), Turnip (Apr 24). Transplant from: Broccoli (Apr 24), Brussel Sprouts (Apr 24), Cabbage (Apr 24), Collards (Apr 24), Kale (Apr 24), Lettuce (Apr 24), +2 more. Plant: Strawberry (Apr 17). |
| May | Start indoors: Cucumber (May 1), Butternut Squash (May 8), Cantaloupe (May 8), Melons (May 8), Pumpkin (May 8), Spaghetti Squash (May 8), +3 more. Direct sow from: Carrots (May 1), Potatoes (May 8), Sunflowers (May 22), Beans (May 29), Pole Beans (May 29). Transplant from: Calendula (May 8), Swiss Chard (May 8), Bok Choy (May 15), Cauliflower (May 15), Cosmos (May 22), Lavender (May 22), +15 more. Last frost around May 22. |
| June | Transplant from: Butternut Squash (Jun 5), Cantaloupe (Jun 5), Cucumber (Jun 5), Eggplant (Jun 5), Melons (Jun 5), Pepper (Jun 5), +6 more. Last sowing dates: Corn (Jun 1), Sunflowers (Jun 13), Brussel Sprouts (Jun 18), Pole Beans (Jun 18), Basil (Jun 23), Cosmos (Jun 23), +9 more. |
| July | Last sowing dates: Marigolds (Jul 3), Parsley (Jul 4), Peas (Jul 9), Cabbage (Jul 18), Carrots (Jul 18), Beets (Jul 19), +8 more. |
| August | Last sowing dates: Kale (Aug 2), Kohlrabi (Aug 2), Turnip (Aug 7), Arugula (Aug 17), Spinach (Aug 17), Radish (Aug 18). |
| September | Direct sow from: Garlic (Sep 19). First frost around September 19. |
| October | Last sowing dates: Garlic (Oct 10). |
| November | Clean up spent plants. Add compost to beds. Rest, review, and plan next year's garden. |
| December | Clean up spent plants. Add compost to beds. Rest, review, and plan next year's garden. |
Frequently Asked Questions
What is the last frost date for Casper, WY (ZIP 82601)?
The median last spring frost date for Casper, WY (ZIP code 82601) is around May 22. This is the 50th-percentile date — meaning half of all years see frost end before this date. Use the 10% and 90% dates to understand the full range of risk in your area. One year in ten frost ends before May 5; one in ten it runs past June 8.
What is the first fall frost date in Casper, WY?
The median first fall frost date for Casper, WY is around September 19. Plan to harvest or protect frost-sensitive crops like tomatoes and peppers at least a week before this date to avoid losses. The first frost arrives around September 10 in the earliest one-in-ten years, so cover tomatoes and peppers from then.
How long is the growing season in Casper, WY?
The frost-free growing season in Casper is about 120 days. This window — from your last spring frost to your first fall frost — is when warm-season vegetables thrive. Cold-hardy crops like kale, spinach, and peas can extend your season by weeks on either side. In Casper (120 frost-free days, a moderate season), 34 of 56 planner crops fit outright, 15 get two plantings, 6 need an indoor start, 1 crop is perennial.
What USDA hardiness zone is Casper, WY?
Casper, WY is in USDA hardiness zone 5a (2023 USDA Plant Hardiness Zone Map). Zones come from the average coldest winter temperature, so they tell you which perennials survive the winter; the frost dates on this page tell you when to plant.
When should I start tomatoes indoors in Casper, WY?
Start tomatoes indoors Apr 17 and plant out Jun 5 in Casper. The planner uses the local median last frost and this crop's indoor-start and transplant offsets.
How many plantings of lettuce fit in Casper?
Two: plant Apr 24 and again by Jul 29; both mature before Sep 26.
When do I plant garlic in Casper?
Sep 19 to Oct 10; it overwinters and is ready the following summer.
Can I grow Butternut Squash in Casper?
Yes, with help. Even planted out Jun 5, the outdoor season is about 15 days short; choose an early variety or grow under cover.
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