Riverton, WY frost dates
Last spring frostMay 12median date
First fall frostSep 24median date
Growing season135 daysfrost-free
Hardiness zone5aZone 5a
How Riverton compares
- In 8 years out of 10, the last spring frost in Riverton falls between May 1 and May 26, a 25-day window. The first fall frost falls between September 11 and October 7.
- The median last frost is 9 days earlier than the Wyoming median of May 21.
- Its 135-day growing season is longer than 67% 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 193 nights a year at or below 32°F.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | May 1 |
| 50% (median) | May 12 |
| 10% (safe for tender plants) | May 26 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 11 |
| 50% (median) | September 24 |
| 90% (late) | October 7 |
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 Riverton, WY
Riverton, WY frost dates — last frost May 12, first frost Sep 24, zone 5a. whenisthelastfrost.com
Crop
JFMAMJJASOND
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: Jul 30 to Aug 27
Start indoors: Mar 17 to Mar 31Transplant outside: Apr 14 to Apr 28Sow outdoors: Apr 14 to Apr 28Plant for fall: Jul 16 to Aug 6
Start indoors: Mar 17 to Mar 31Transplant outside: Apr 28 to May 12Plant for fall: Jun 18 to Jul 9
Start indoors: Mar 17 to Mar 31Transplant outside: Apr 21 to May 5Plant for fall: Jun 18 to Jul 9
Start indoors: Mar 17 to Mar 31Transplant outside: Apr 28 to May 12Plant for fall: Jun 18 to Jul 9
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 2 to Jul 23
Sow outdoors: Mar 31 to Apr 21Plant for fall: Jul 30 to Aug 20
Sow outdoors: Apr 7 to May 19Plant for fall: Aug 13 to Sep 3
Start indoors: Apr 14 to Apr 21Transplant outside: May 26 to Jun 2Sow outdoors: May 19 to Jun 2Plant for fall: Jul 9 to Jul 23
Start indoors: Apr 14 to Apr 21Sow 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 2
Start indoors: Apr 14 to Apr 21Transplant outside: May 26 to Jun 9
Sow outdoors: Apr 21 to May 19Plant for fall: Jul 2 to Jul 16
Sow outdoors: Apr 21 to May 19Plant for fall: Jul 16 to Jul 30
Sow outdoors: Apr 21 to May 12
Sow outdoors: Apr 28 to May 26Plant for fall: Jul 16 to Jul 30
Sow outdoors: Apr 28 to May 19Plant for fall: Jul 30 to Aug 20
Sow outdoors: May 19 to Jun 9Plant for fall: Jul 9 to Jul 23
Sow outdoors: May 19 to Jun 2
Transplant outside: May 26 to Jun 16
Plant for fall: Sep 10 to Oct 15
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Riverton, 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 | Jul 30 – Aug 27 |
| Kale | Mar 17 – Mar 31 | Apr 14 – Apr 28 | Apr 14 – Apr 28 | Jul 16 – Aug 6 |
| Broccoli | Mar 17 – Mar 31 | Apr 28 – May 12 | — | Jun 18 – Jul 9 |
| Cabbage | Mar 17 – Mar 31 | Apr 21 – May 5 | — | Jun 18 – Jul 9 |
| Cauliflower | Mar 17 – Mar 31 | Apr 28 – May 12 | — | Jun 18 – Jul 9 |
| 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 2 – Jul 23 |
| Spinach | — | — | Mar 31 – Apr 21 | Jul 30 – Aug 20 |
| Radishes | — | — | Apr 7 – May 19 | Aug 13 – Sep 3 |
| Cucumbers | Apr 14 – Apr 21 | May 26 – Jun 2 | May 19 – Jun 2 | Jul 9 – Jul 23 |
| Zucchini & Summer Squash | Apr 14 – Apr 21 | — | May 19 – Jun 2 | Jul 16 – Jul 30 |
| 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 2 – Jul 16 |
| Beets | — | — | Apr 21 – May 19 | Jul 16 – Jul 30 |
| Potatoes | — | — | Apr 21 – May 12 | — |
| Swiss Chard | — | — | Apr 28 – May 26 | Jul 16 – Jul 30 |
| Cilantro | — | — | Apr 28 – May 19 | Jul 30 – Aug 20 |
| Green Beans | — | — | May 19 – Jun 9 | Jul 9 – Jul 23 |
| Sweet Corn | — | — | May 19 – Jun 2 | — |
| Sweet Potatoes | — | May 26 – Jun 16 | — | — |
| Garlic | — | — | — | Sep 10 – Oct 15 |
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 Riverton, WY weather station, 14 km away (elevation 4,954 ft (1,510 m)).
Frost dates near Riverton
- Saint Stephens May 12 · Sep 24
- Shoshoni May 7 · Oct 3
- Arapahoe May 16 · Sep 28
- Lander May 18 · Sep 27
- Hudson May 18 · Sep 27
- Pavillion May 14 · Sep 30
- Lysite May 14 · Oct 3
- Fort Washakie May 18 · Sep 27
- Jeffrey City Jun 1 · Sep 13
- Kinnear May 21 · Sep 20
Frequently asked questions
When is the last frost in Riverton, WY?
The median last spring frost in Riverton, 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 Riverton, WY?
The median first fall frost is September 24, with about a 10% chance of frost before September 11.
How long is the growing season in Riverton, WY?
About 135 days between the median last spring frost and first fall frost.
What planting zone is Riverton, WY?
Riverton, WY is in USDA hardiness zone 5a.