Osage, WY frost dates
Last spring frostMay 20median date
First fall frostSep 23median date
Growing season126 daysfrost-free
Hardiness zone4bZone 4b
How Osage compares
- In 8 years out of 10, the last spring frost in Osage falls between May 8 and June 4, a 27-day window. The first fall frost falls between September 7 and October 5.
- The median last frost is 1 day earlier than the Wyoming median of May 21.
- Its 126-day growing season is longer than 50% of the 153 Wyoming places with a regular frost season (state median 125 days).
- The last frost is 12 days later than the zone 4b median of May 8. Hardiness zones measure winter cold, not season length, so use these dates rather than a zone 4b chart.
- The weather station records an average of 182 nights a year at or below 32°F.
- Compared with Rapid City, SD, 93 km away, the last frost here is 17 days later than there and the growing season is 32 days shorter.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | May 8 |
| 50% (median) | May 20 |
| 10% (safe for tender plants) | June 4 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 7 |
| 50% (median) | September 23 |
| 90% (late) | October 5 |
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 Osage, WY
Osage, WY frost dates — last frost May 20, first frost Sep 23, zone 4b. whenisthelastfrost.com
Crop
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Start indoors: Feb 25 to Mar 11Transplant outside: Apr 22 to May 6
Start indoors: Mar 11 to Mar 25Transplant outside: Jun 3 to Jun 17
Start indoors: Mar 11 to Mar 25Transplant outside: Jun 3 to Jun 17
Start indoors: Mar 25 to Apr 8Transplant outside: May 27 to Jun 10
Start indoors: Mar 25 to Apr 8Transplant outside: Apr 29 to May 13Sow outdoors: Apr 22 to May 27Plant for fall: Jul 29 to Aug 26
Start indoors: Mar 25 to Apr 8Transplant outside: Apr 22 to May 6Sow outdoors: Apr 22 to May 6Plant for fall: Jul 15 to Aug 5
Start indoors: Mar 25 to Apr 8Transplant outside: May 6 to May 20Plant for fall: Jun 17 to Jul 8
Start indoors: Mar 25 to Apr 8Transplant outside: Apr 29 to May 13Plant for fall: Jun 17 to Jul 8
Start indoors: Mar 25 to Apr 8Transplant outside: May 6 to May 20Plant for fall: Jun 17 to Jul 8
Start indoors: Apr 8 to Apr 22Transplant outside: Jun 10 to Jun 24Sow outdoors: Jun 10 to Jun 24
Start indoors: Apr 8 to Apr 22Transplant outside: May 27 to Jun 10
Sow outdoors: Apr 8 to Apr 29Plant for fall: Jul 1 to Jul 22
Sow outdoors: Apr 8 to Apr 29Plant for fall: Jul 29 to Aug 19
Sow outdoors: Apr 15 to May 27Plant for fall: Aug 12 to Sep 2
Start indoors: Apr 22 to Apr 29Transplant outside: Jun 3 to Jun 10Sow outdoors: May 27 to Jun 10Plant for fall: Jul 8 to Jul 22
Start indoors: Apr 22 to Apr 29Sow outdoors: May 27 to Jun 10Plant for fall: Jul 15 to Jul 29
Start indoors: Apr 22 to Apr 29Sow outdoors: May 27 to Jun 10
Start indoors: Apr 22 to Apr 29Transplant outside: Jun 3 to Jun 17
Sow outdoors: Apr 29 to May 27Plant for fall: Jul 1 to Jul 15
Sow outdoors: Apr 29 to May 27Plant for fall: Jul 15 to Jul 29
Sow outdoors: Apr 29 to May 20
Sow outdoors: May 6 to Jun 3Plant for fall: Jul 15 to Jul 29
Sow outdoors: May 6 to May 27Plant for fall: Jul 29 to Aug 19
Sow outdoors: May 27 to Jun 17Plant for fall: Jul 8 to Jul 22
Sow outdoors: May 27 to Jun 10
Transplant outside: Jun 3 to Jun 24
Plant for fall: Sep 9 to Oct 14
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Osage, WY
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Feb 25 – Mar 11 | Apr 22 – May 6 | — | — |
| Peppers | Mar 11 – Mar 25 | Jun 3 – Jun 17 | — | — |
| Eggplant | Mar 11 – Mar 25 | Jun 3 – Jun 17 | — | — |
| Tomatoes | Mar 25 – Apr 8 | May 27 – Jun 10 | — | — |
| Lettuce | Mar 25 – Apr 8 | Apr 29 – May 13 | Apr 22 – May 27 | Jul 29 – Aug 26 |
| Kale | Mar 25 – Apr 8 | Apr 22 – May 6 | Apr 22 – May 6 | Jul 15 – Aug 5 |
| Broccoli | Mar 25 – Apr 8 | May 6 – May 20 | — | Jun 17 – Jul 8 |
| Cabbage | Mar 25 – Apr 8 | Apr 29 – May 13 | — | Jun 17 – Jul 8 |
| Cauliflower | Mar 25 – Apr 8 | May 6 – May 20 | — | Jun 17 – Jul 8 |
| Okra | Apr 8 – Apr 22 | Jun 10 – Jun 24 | Jun 10 – Jun 24 | — |
| Basil | Apr 8 – Apr 22 | May 27 – Jun 10 | — | — |
| Peas | — | — | Apr 8 – Apr 29 | Jul 1 – Jul 22 |
| Spinach | — | — | Apr 8 – Apr 29 | Jul 29 – Aug 19 |
| Radishes | — | — | Apr 15 – May 27 | Aug 12 – Sep 2 |
| Cucumbers | Apr 22 – Apr 29 | Jun 3 – Jun 10 | May 27 – Jun 10 | Jul 8 – Jul 22 |
| Zucchini & Summer Squash | Apr 22 – Apr 29 | — | May 27 – Jun 10 | Jul 15 – Jul 29 |
| Winter Squash & Pumpkins | Apr 22 – Apr 29 | — | May 27 – Jun 10 | — |
| Melons & Watermelon | Apr 22 – Apr 29 | Jun 3 – Jun 17 | — | — |
| Carrots | — | — | Apr 29 – May 27 | Jul 1 – Jul 15 |
| Beets | — | — | Apr 29 – May 27 | Jul 15 – Jul 29 |
| Potatoes | — | — | Apr 29 – May 20 | — |
| Swiss Chard | — | — | May 6 – Jun 3 | Jul 15 – Jul 29 |
| Cilantro | — | — | May 6 – May 27 | Jul 29 – Aug 19 |
| Green Beans | — | — | May 27 – Jun 17 | Jul 8 – Jul 22 |
| Sweet Corn | — | — | May 27 – Jun 10 | — |
| Sweet Potatoes | — | Jun 3 – Jun 24 | — | — |
| Garlic | — | — | — | Sep 9 – Oct 14 |
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 Upton, WY weather station, 18 km away (elevation 4,321 ft (1,317 m)).
Frost dates near Osage
- Upton May 20 · Sep 23
- Newcastle May 13 · Oct 3
- Four Corners May 13 · Oct 3
- Sundance May 21 · Sep 25
- Moorcroft May 23 · Sep 20
- Devils Tower May 23 · Sep 20
- Beulah May 17 · Sep 27
- Rozet May 15 · Oct 1
- Alva May 17 · Sep 23
- Hulett May 17 · Sep 23
Frequently asked questions
When is the last frost in Osage, WY?
The median last spring frost in Osage, WY is May 20. There is still about a 10% chance of frost after June 4, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Osage, WY?
The median first fall frost is September 23, with about a 10% chance of frost before September 7.
How long is the growing season in Osage, WY?
About 126 days between the median last spring frost and first fall frost.
What planting zone is Osage, WY?
Osage, WY is in USDA hardiness zone 4b.