Frost dates for 82609 — Casper, WY
Last spring frostMay 12median date
First fall frostOct 1median date
Growing season142 daysfrost-free
Hardiness zone5aZone 5a
How Casper compares
- In 8 years out of 10, the last spring frost in Casper falls between April 28 and May 26, a 28-day window. The first fall frost falls between September 18 and October 19.
- The median last frost is 9 days earlier than the Wyoming median of May 21.
- Its 142-day growing season is longer than 83% of the 153 Wyoming places with a regular frost season (state median 125 days).
- The last frost is 9 days later than the zone 5a median of May 3. Hardiness zones measure winter cold, not season length, so use these dates rather than a zone 5a chart.
- The weather station records an average of 156 nights a year at or below 32°F.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | April 28 |
| 50% (median) | May 12 |
| 10% (safe for tender plants) | May 26 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 18 |
| 50% (median) | October 1 |
| 90% (late) | October 19 |
Frost here means 32°F (0°C). A median date means half of years have their last frost earlier and half later.
Planting calendar for Casper, WY
Frost dates for 82609 — Casper, WY — last frost May 12, first frost Oct 1, zone 5a. whenisthelastfrost.com
Crop
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Start indoors: Feb 17 to Mar 3Transplant outside: Apr 14 to Apr 28
Start indoors: Mar 3 to Mar 17Transplant outside: May 26 to Jun 9
Start indoors: Mar 3 to Mar 17Transplant outside: May 26 to Jun 9
Start indoors: Mar 17 to Mar 31Transplant outside: May 19 to Jun 2
Start indoors: Mar 17 to Mar 31Transplant outside: Apr 21 to May 5Sow outdoors: Apr 14 to May 19Plant for fall: Aug 6 to Sep 3
Start indoors: Mar 17 to Mar 31Transplant outside: Apr 14 to Apr 28Sow outdoors: Apr 14 to Apr 28Plant for fall: Jul 23 to Aug 13
Start indoors: Mar 17 to Mar 31Transplant outside: Apr 28 to May 12Plant for fall: Jun 25 to Jul 16
Start indoors: Mar 17 to Mar 31Transplant outside: Apr 21 to May 5Plant for fall: Jun 25 to Jul 16
Start indoors: Mar 17 to Mar 31Transplant outside: Apr 28 to May 12Plant for fall: Jun 25 to Jul 16
Start indoors: Mar 31 to Apr 14Transplant outside: Jun 2 to Jun 16Sow outdoors: Jun 2 to Jun 16
Start indoors: Mar 31 to Apr 14Transplant outside: May 19 to Jun 2
Sow outdoors: Mar 31 to Apr 21Plant for fall: Jul 9 to Jul 30
Sow outdoors: Mar 31 to Apr 21Plant for fall: Aug 6 to Aug 27
Sow outdoors: Apr 7 to May 19Plant for fall: Aug 20 to Sep 10
Start indoors: Apr 14 to Apr 21Transplant outside: May 26 to Jun 2Sow outdoors: May 19 to Jun 2Plant for fall: Jul 16 to Jul 30
Start indoors: Apr 14 to Apr 21Sow outdoors: May 19 to Jun 2Plant for fall: Jul 23 to Aug 6
Start indoors: Apr 14 to Apr 21Sow outdoors: May 19 to Jun 2
Start indoors: Apr 14 to Apr 21Transplant outside: May 26 to Jun 9
Sow outdoors: Apr 21 to May 19Plant for fall: Jul 9 to Jul 23
Sow outdoors: Apr 21 to May 19Plant for fall: Jul 23 to Aug 6
Sow outdoors: Apr 21 to May 12
Sow outdoors: Apr 28 to May 26Plant for fall: Jul 23 to Aug 6
Sow outdoors: Apr 28 to May 19Plant for fall: Aug 6 to Aug 27
Sow outdoors: May 19 to Jun 9Plant for fall: Jul 16 to Jul 30
Sow outdoors: May 19 to Jun 2
Transplant outside: May 26 to Jun 16
Plant for fall: Sep 17 to Oct 22
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Casper, WY
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Feb 17 – Mar 3 | Apr 14 – Apr 28 | — | — |
| Peppers | Mar 3 – Mar 17 | May 26 – Jun 9 | — | — |
| Eggplant | Mar 3 – Mar 17 | May 26 – Jun 9 | — | — |
| Tomatoes | Mar 17 – Mar 31 | May 19 – Jun 2 | — | — |
| Lettuce | Mar 17 – Mar 31 | Apr 21 – May 5 | Apr 14 – May 19 | Aug 6 – Sep 3 |
| Kale | Mar 17 – Mar 31 | Apr 14 – Apr 28 | Apr 14 – Apr 28 | Jul 23 – Aug 13 |
| Broccoli | Mar 17 – Mar 31 | Apr 28 – May 12 | — | Jun 25 – Jul 16 |
| Cabbage | Mar 17 – Mar 31 | Apr 21 – May 5 | — | Jun 25 – Jul 16 |
| Cauliflower | Mar 17 – Mar 31 | Apr 28 – May 12 | — | Jun 25 – Jul 16 |
| Okra | Mar 31 – Apr 14 | Jun 2 – Jun 16 | Jun 2 – Jun 16 | — |
| Basil | Mar 31 – Apr 14 | May 19 – Jun 2 | — | — |
| Peas | — | — | Mar 31 – Apr 21 | Jul 9 – Jul 30 |
| Spinach | — | — | Mar 31 – Apr 21 | Aug 6 – Aug 27 |
| Radishes | — | — | Apr 7 – May 19 | Aug 20 – Sep 10 |
| Cucumbers | Apr 14 – Apr 21 | May 26 – Jun 2 | May 19 – Jun 2 | Jul 16 – Jul 30 |
| Zucchini & Summer Squash | Apr 14 – Apr 21 | — | May 19 – Jun 2 | Jul 23 – Aug 6 |
| Winter Squash & Pumpkins | Apr 14 – Apr 21 | — | May 19 – Jun 2 | — |
| Melons & Watermelon | Apr 14 – Apr 21 | May 26 – Jun 9 | — | — |
| Carrots | — | — | Apr 21 – May 19 | Jul 9 – Jul 23 |
| Beets | — | — | Apr 21 – May 19 | Jul 23 – Aug 6 |
| Potatoes | — | — | Apr 21 – May 12 | — |
| Swiss Chard | — | — | Apr 28 – May 26 | Jul 23 – Aug 6 |
| Cilantro | — | — | Apr 28 – May 19 | Aug 6 – Aug 27 |
| Green Beans | — | — | May 19 – Jun 9 | Jul 16 – Jul 30 |
| Sweet Corn | — | — | May 19 – Jun 2 | — |
| Sweet Potatoes | — | May 26 – Jun 16 | — | — |
| Garlic | — | — | — | Sep 17 – Oct 22 |
Dates come from the median frost dates and common extension-service timing. Adjust for your soil temperature, microclimate and the varieties you grow.
About these dates
Based on 1991–2020 NOAA climate normals for the Casper 1sw, WY weather station, about 1 km away (elevation 5,144 ft (1,568 m)).
ZIP codes in Casper: 82601 82602 82604 82605 82609
Frost dates near Casper
- Mills May 10 · Sep 29
- Evansville May 12 · Oct 1
- Glenrock May 12 · Oct 1
- Natrona May 23 · Sep 20
- Alcova May 9 · Oct 7
- Powder River May 23 · Sep 20
- Edgerton May 22 · Sep 22
- Midwest May 22 · Sep 22
Frequently asked questions
When is the last frost in Casper, WY?
The median last spring frost in Casper, WY is May 12. There is still about a 10% chance of frost after May 26, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Casper, WY?
The median first fall frost is October 1, with about a 10% chance of frost before September 18.
How long is the growing season in Casper, WY?
About 142 days between the median last spring frost and first fall frost.
What planting zone is Casper, WY?
Casper, WY is in USDA hardiness zone 5a.