Casper, Wyoming planting calendar and frost dates
Casper is in USDA hardiness zone 5a. The last spring frost typically comes around May 26 and the first fall frost around September 22, giving about 117 frost-free days a year.
- Hardiness zone
- Zone 5a
- Typical last frost
- May 26
- Typical first frost
- September 22
- Frost-free season
- 117 days
Frost dates in Casper
Last spring frost
- May 12Risky: frost later than this in 9 years out of 10
- May 26Typical: a later frost in half of years
- June 10Safe: a later frost only 1 year in 10
First fall frost
- September 5Risky: frost earlier than this 1 year in 10
- September 22Typical: an earlier frost in half of years
- October 4Late: frost before this in 9 years out of 10
The growing season between the typical last and first frosts is about 117 days. Frost here means a low of 32°F at the weather station. A hard freeze (28°F), which damages most hardy crops too, typically ends around May 11 and returns around October 2.
NOAA U.S. Climate Normals 1991-2020 for Casper Natrona Co Airport, 7.9 miles WNW of the city center and 233 feet higher. Low-lying and rural spots often frost later in spring and earlier in fall than airports and city centers.
What to plant each month in Casper
February
Start indoors: onions
March
Start indoors: black-eyed susans, broccoli, cabbages, cauliflower, chives, collard greens, ginger, kale, leeks, lettuce, marigolds, onions, oregano, parsley, peppers, petunias, ranunculus, rosemary, sage, snapdragons
April
Start indoors: basil, black-eyed susans, cabbages, cauliflower, celery, chives, cilantro, collard greens, eggplants, ginger, lettuce, marigolds, nasturtiums, peppers, ranunculus, sage, snapdragons, spinach, swiss chard, tomatoes
Plant or sow outdoors: beets, black-eyed susans, blackberries, blueberries, broccoli, cauliflower, chives, cilantro, collard greens, figs, garlic, gladioli, grapes, grass seed, hollyhocks, kale, leeks, onions, peas, poppies, radishes, ranunculus, raspberries, rhubarb, roses, spinach, strawberries, swiss chard, turnips, wildflowers
May
Start indoors: basil, cantaloupes, cosmos, cucumbers, okra, pumpkins, ranunculus, watermelons, winter squash, zucchini
Plant or sow outdoors: asparagus, beets, black-eyed susans, blackberries, broccoli, cabbages, carrots, cauliflower, chives, cilantro, collard greens, dahlias, dill, figs, garden mums, gladioli, grapes, green onions, kentucky bluegrass, lavenders, leeks, lettuce, lilies, marigolds, mints, nasturtiums, onions, oregano, parsley, perennial ryegrass, petunias, potatoes, radishes, ranunculus, rosemary, roses, sage, snapdragons, spinach, sunflowers, sweet corn, sweet peas, swiss chard, tall fescue, thyme, turnips
June
Start indoors: zinnias
Plant or sow outdoors: asparagus, basil, bermudagrass, cantaloupes, celery, centipedegrass, chives, cilantro, cosmos, cucumbers, dahlias, dill, eggplants, garden mums, ginger, gladioli, grapes, green beans, green onions, kentucky bluegrass, lavenders, lettuce, lilies, marigolds, mints, nasturtiums, okra, oregano, parsley, peanuts, peppers, perennial ryegrass, petunias, pumpkins, ranunculus, rosemary, sage, spinach, st. augustinegrass, sunflowers, sweet corn, sweet peas, sweet potatoes, swiss chard, tall fescue, thyme, tomatoes, watermelons, winter squash, zoysiagrass, zucchini
Plant for fall: bearded irises, brussels sprouts, carrots, collard greens, lettuce, peas, snapdragons, swiss chard
July
Plant or sow outdoors: bermudagrass, celery, centipedegrass, cosmos, green onions, okra, peanuts, st. augustinegrass, sweet potatoes, zinnias, zoysiagrass
Plant for fall: azaleas, bearded irises, beets, broccoli, cabbages, carrots, cauliflower, clematis, collard greens, coneflowers, daylilies, hostas, hydrangeas, kale, lettuce, peas, radishes, roses, saffron, snapdragons, spinach, swiss chard, turnips
August
Plant or sow outdoors: bermudagrass, centipedegrass, st. augustinegrass, zoysiagrass
Plant for fall: azaleas, bearded irises, beets, broccoli, cabbages, cauliflower, clematis, coneflowers, crocuses, daffodils, daylilies, grass seed, hostas, hyacinths, hydrangeas, kale, lilies, ornamental alliums, peonies, radishes, roses, saffron, spinach, tulips, turnips
September
Plant for fall: crocuses, daffodils, daylilies, garlic, hyacinths, lilies, ornamental alliums, peonies, tulips
October
Plant for fall: crocuses, garlic, hyacinths, ornamental alliums, tulips
Frost dates and zones by ZIP code in Casper
All 3 of Casper's main ZIP codes take their frost dates from Casper Natrona Co Airport, so the dates on this page apply across the city. Every one of them is in zone 5a.
Planting dates for popular crops in Casper
| Plant | Start indoors | Plant or sow outdoors | Fall planting |
|---|---|---|---|
| Tomatoes | Apr 13 to 27 | Jun 8 to 22 | — |
| Strawberries | — | Apr 14 to 28 | — |
| Lettuce | Mar 31 to Apr 14 | May 19 to Jun 2 | Jun 23 to Jul 28 |
| Cilantro | Apr 14 to 28 | May 26 to Jun 2 | — |
| Basil | Apr 20 to May 4 | Jun 8 to 15 | — |
| Potatoes | — | May 11 to 18 | — |
| Garlic | — | Apr 14 to 28 | Sep 22 to Oct 6 |
| Onions | Feb 3 to Mar 17 | Apr 28 to May 12 | — |
| Cucumbers | May 11 to 25 | Jun 8 to 22 | — |
| Pumpkins | May 12 to 26 | Jun 9 to 23 | — |
| Peppers | Mar 23 to Apr 20 | Jun 8 to 22 | — |
| Carrots | — | May 5 to 26 | Jun 30 to Jul 21 |
| Sweet Potatoes | — | Jun 24 to Jul 1 | — |
| Watermelons | May 4 to 18 | Jun 8 to 22 | — |
| Sweet Corn | — | May 26 to Jun 9 | — |
| Green Beans | — | Jun 8 to 22 | — |
| Zucchini | May 11 to 25 | Jun 8 to 22 | — |
| Broccoli | Mar 10 to 31 | Apr 28 to May 12 | Jul 7 to Aug 4 |
| Peas | — | Apr 14 to 28 | Jun 30 to Jul 14 |
| Spinach | Apr 14 to 21 | May 19 to Jun 2 | Jul 14 to Aug 18 |
| Sunflowers | — | May 26 to Jun 16 | — |
| Zinnias | Jun 11 to 18 | Jul 9 to 23 | — |
| Tulips | — | — | Aug 11 to Oct 6 |
| Daffodils | — | — | Aug 11 to Sep 22 |
| Grass Seed | — | Apr 14 to 28 | Aug 11 to 25 |
Nearby cities
- Cheyenne, WY zone 5b, last frost May 12
- Fort Collins, CO zone 5b, last frost May 2
- Rapid City, SD zone 5b, last frost May 3
- Loveland, CO zone 5b, last frost May 21
- Greeley, CO zone 5b, last frost May 2
- Longmont, CO zone 5b, last frost May 6
Planting in WyomingAbout zone 5aPrintable calendar for Casper
Questions
When is the last frost in Casper?
Around May 26 in a typical year, based on NOAA's 1991-2020 records for Casper Natrona Co Airport. There is still a 1 in 10 chance of frost after June 10.
What planting zone is Casper in?
USDA hardiness zone 5a (2023 map). The zone tells you which perennials survive the winter; planting dates depend on frost dates instead.
When should I plant tomatoes in Casper?
Start seeds indoors April 13 to 27 and set plants out June 8 to 22; the safest date to plant out is after June 10.
When is the first frost in Casper?
Around September 22 in a typical year, and before September 5 about 1 year in 10.