Ralston, WY frost dates
Last spring frostMay 15median date
First fall frostSep 25median date
Growing season133 daysfrost-free
Hardiness zone5aZone 5a
How Ralston compares
- In 8 years out of 10, the last spring frost in Ralston falls between May 1 and June 1, a 31-day window. The first fall frost falls between September 11 and October 10.
- The median last frost is 6 days earlier than the Wyoming median of May 21.
- Its 133-day growing season is longer than 64% of the 153 Wyoming places with a regular frost season (state median 125 days).
- The last frost is 12 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 173 nights a year at or below 32°F.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | May 1 |
| 50% (median) | May 15 |
| 10% (safe for tender plants) | June 1 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 11 |
| 50% (median) | September 25 |
| 90% (late) | October 10 |
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 Ralston, WY
Ralston, WY frost dates — last frost May 15, first frost Sep 25, zone 5a. whenisthelastfrost.com
Crop
JFMAMJJASOND
Start indoors: Feb 20 to Mar 6Transplant outside: Apr 17 to May 1
Start indoors: Mar 6 to Mar 20Transplant outside: May 29 to Jun 12
Start indoors: Mar 6 to Mar 20Transplant outside: May 29 to Jun 12
Start indoors: Mar 20 to Apr 3Transplant outside: May 22 to Jun 5
Start indoors: Mar 20 to Apr 3Transplant outside: Apr 24 to May 8Sow outdoors: Apr 17 to May 22Plant for fall: Jul 31 to Aug 28
Start indoors: Mar 20 to Apr 3Transplant outside: Apr 17 to May 1Sow outdoors: Apr 17 to May 1Plant for fall: Jul 17 to Aug 7
Start indoors: Mar 20 to Apr 3Transplant outside: May 1 to May 15Plant for fall: Jun 19 to Jul 10
Start indoors: Mar 20 to Apr 3Transplant outside: Apr 24 to May 8Plant for fall: Jun 19 to Jul 10
Start indoors: Mar 20 to Apr 3Transplant outside: May 1 to May 15Plant for fall: Jun 19 to Jul 10
Start indoors: Apr 3 to Apr 17Transplant outside: Jun 5 to Jun 19Sow outdoors: Jun 5 to Jun 19
Start indoors: Apr 3 to Apr 17Transplant outside: May 22 to Jun 5
Sow outdoors: Apr 3 to Apr 24Plant for fall: Jul 3 to Jul 24
Sow outdoors: Apr 3 to Apr 24Plant for fall: Jul 31 to Aug 21
Sow outdoors: Apr 10 to May 22Plant for fall: Aug 14 to Sep 4
Start indoors: Apr 17 to Apr 24Transplant outside: May 29 to Jun 5Sow outdoors: May 22 to Jun 5Plant for fall: Jul 10 to Jul 24
Start indoors: Apr 17 to Apr 24Sow outdoors: May 22 to Jun 5Plant for fall: Jul 17 to Jul 31
Start indoors: Apr 17 to Apr 24Sow outdoors: May 22 to Jun 5
Start indoors: Apr 17 to Apr 24Transplant outside: May 29 to Jun 12
Sow outdoors: Apr 24 to May 22Plant for fall: Jul 3 to Jul 17
Sow outdoors: Apr 24 to May 22Plant for fall: Jul 17 to Jul 31
Sow outdoors: Apr 24 to May 15
Sow outdoors: May 1 to May 29Plant for fall: Jul 17 to Jul 31
Sow outdoors: May 1 to May 22Plant for fall: Jul 31 to Aug 21
Sow outdoors: May 22 to Jun 12Plant for fall: Jul 10 to Jul 24
Sow outdoors: May 22 to Jun 5
Transplant outside: May 29 to Jun 19
Plant for fall: Sep 11 to Oct 16
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Ralston, WY
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Feb 20 – Mar 6 | Apr 17 – May 1 | — | — |
| Peppers | Mar 6 – Mar 20 | May 29 – Jun 12 | — | — |
| Eggplant | Mar 6 – Mar 20 | May 29 – Jun 12 | — | — |
| Tomatoes | Mar 20 – Apr 3 | May 22 – Jun 5 | — | — |
| Lettuce | Mar 20 – Apr 3 | Apr 24 – May 8 | Apr 17 – May 22 | Jul 31 – Aug 28 |
| Kale | Mar 20 – Apr 3 | Apr 17 – May 1 | Apr 17 – May 1 | Jul 17 – Aug 7 |
| Broccoli | Mar 20 – Apr 3 | May 1 – May 15 | — | Jun 19 – Jul 10 |
| Cabbage | Mar 20 – Apr 3 | Apr 24 – May 8 | — | Jun 19 – Jul 10 |
| Cauliflower | Mar 20 – Apr 3 | May 1 – May 15 | — | Jun 19 – Jul 10 |
| Okra | Apr 3 – Apr 17 | Jun 5 – Jun 19 | Jun 5 – Jun 19 | — |
| Basil | Apr 3 – Apr 17 | May 22 – Jun 5 | — | — |
| Peas | — | — | Apr 3 – Apr 24 | Jul 3 – Jul 24 |
| Spinach | — | — | Apr 3 – Apr 24 | Jul 31 – Aug 21 |
| Radishes | — | — | Apr 10 – May 22 | Aug 14 – Sep 4 |
| Cucumbers | Apr 17 – Apr 24 | May 29 – Jun 5 | May 22 – Jun 5 | Jul 10 – Jul 24 |
| Zucchini & Summer Squash | Apr 17 – Apr 24 | — | May 22 – Jun 5 | Jul 17 – Jul 31 |
| Winter Squash & Pumpkins | Apr 17 – Apr 24 | — | May 22 – Jun 5 | — |
| Melons & Watermelon | Apr 17 – Apr 24 | May 29 – Jun 12 | — | — |
| Carrots | — | — | Apr 24 – May 22 | Jul 3 – Jul 17 |
| Beets | — | — | Apr 24 – May 22 | Jul 17 – Jul 31 |
| Potatoes | — | — | Apr 24 – May 15 | — |
| Swiss Chard | — | — | May 1 – May 29 | Jul 17 – Jul 31 |
| Cilantro | — | — | May 1 – May 22 | Jul 31 – Aug 21 |
| Green Beans | — | — | May 22 – Jun 12 | Jul 10 – Jul 24 |
| Sweet Corn | — | — | May 22 – Jun 5 | — |
| Sweet Potatoes | — | May 29 – Jun 19 | — | — |
| Garlic | — | — | — | Sep 11 – Oct 16 |
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 Heart Mtn, WY weather station, 7 km away (elevation 4,790 ft (1,460 m)).
Frost dates near Ralston
- Powell May 19 · Sep 20
- Byron May 9 · Sep 29
- Cody May 12 · Oct 1
- Deaver May 6 · Oct 1
- Frannie May 6 · Oct 1
- Cowley May 9 · Sep 29
- Lovell May 9 · Sep 29
- Emblem May 12 · Sep 28
- Burlington May 12 · Sep 28
- Wapiti May 27 · Sep 25
Frequently asked questions
When is the last frost in Ralston, WY?
The median last spring frost in Ralston, WY is May 15. There is still about a 10% chance of frost after June 1, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Ralston, WY?
The median first fall frost is September 25, with about a 10% chance of frost before September 11.
How long is the growing season in Ralston, WY?
About 133 days between the median last spring frost and first fall frost.
What planting zone is Ralston, WY?
Ralston, WY is in USDA hardiness zone 5a.