Plymouth, WA frost dates
Last spring frostMar 27median date
First fall frostNov 4median date
Growing season222 daysfrost-free
Hardiness zone7bZone 7b
How Plymouth compares
- In 8 years out of 10, the last spring frost in Plymouth falls between March 8 and April 14, a 37-day window. The first fall frost falls between October 21 and November 22.
- The median last frost is 25 days earlier than the Washington median of Apr 21.
- Its 222-day growing season is longer than 76% of the 491 Washington places with a regular frost season (state median 182 days).
- The last frost is 9 days earlier than the zone 7b median of Apr 5. Hardiness zones measure winter cold, not season length, so use these dates rather than a zone 7b chart.
- The weather station records an average of 67 nights a year at or below 32°F.
- Compared with Kennewick, WA, 33 km away, the last frost here is 1 day earlier than there and the growing season is 6 days longer.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | March 8 |
| 50% (median) | March 27 |
| 10% (safe for tender plants) | April 14 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | October 21 |
| 50% (median) | November 4 |
| 90% (late) | November 22 |
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 Plymouth, WA
Plymouth, WA frost dates — last frost Mar 27, first frost Nov 4, zone 7b. whenisthelastfrost.com
Crop
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Start indoors: Jan 2 to Jan 16Transplant outside: Feb 27 to Mar 13
Start indoors: Jan 16 to Jan 30Transplant outside: Apr 10 to Apr 24
Start indoors: Jan 16 to Jan 30Transplant outside: Apr 10 to Apr 24
Start indoors: Jan 30 to Feb 13Transplant outside: Apr 3 to Apr 17
Start indoors: Jan 30 to Feb 13Transplant outside: Mar 6 to Mar 20Sow outdoors: Feb 27 to Apr 3Plant for fall: Sep 9 to Oct 7
Start indoors: Jan 30 to Feb 13Transplant outside: Feb 27 to Mar 13Sow outdoors: Feb 27 to Mar 13Plant for fall: Aug 26 to Sep 16
Start indoors: Jan 30 to Feb 13Transplant outside: Mar 13 to Mar 27Plant for fall: Jul 29 to Aug 19
Start indoors: Jan 30 to Feb 13Transplant outside: Mar 6 to Mar 20Plant for fall: Jul 29 to Aug 19
Start indoors: Jan 30 to Feb 13Transplant outside: Mar 13 to Mar 27Plant for fall: Jul 29 to Aug 19
Start indoors: Feb 13 to Feb 27Transplant outside: Apr 17 to May 1Sow outdoors: Apr 17 to May 1
Start indoors: Feb 13 to Feb 27Transplant outside: Apr 3 to Apr 17
Sow outdoors: Feb 13 to Mar 6Plant for fall: Aug 12 to Sep 2
Sow outdoors: Feb 13 to Mar 6Plant for fall: Sep 9 to Sep 30
Sow outdoors: Feb 20 to Apr 3Plant for fall: Sep 23 to Oct 14
Start indoors: Feb 27 to Mar 6Transplant outside: Apr 10 to Apr 17Sow outdoors: Apr 3 to Apr 17Plant for fall: Aug 19 to Sep 2
Start indoors: Feb 27 to Mar 6Sow outdoors: Apr 3 to Apr 17Plant for fall: Aug 26 to Sep 9
Start indoors: Feb 27 to Mar 6Sow outdoors: Apr 3 to Apr 17
Start indoors: Feb 27 to Mar 6Transplant outside: Apr 10 to Apr 24
Sow outdoors: Mar 6 to Apr 3Plant for fall: Aug 12 to Aug 26
Sow outdoors: Mar 6 to Apr 3Plant for fall: Aug 26 to Sep 9
Sow outdoors: Mar 6 to Mar 27
Sow outdoors: Mar 13 to Apr 10Plant for fall: Aug 26 to Sep 9
Sow outdoors: Mar 13 to Apr 3Plant for fall: Sep 9 to Sep 30
Sow outdoors: Apr 3 to Apr 24Plant for fall: Aug 19 to Sep 2
Sow outdoors: Apr 3 to Apr 17
Transplant outside: Apr 10 to May 1
Plant for fall: Oct 21 to Nov 25
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Plymouth, WA
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Jan 2 – Jan 16 | Feb 27 – Mar 13 | — | — |
| Peppers | Jan 16 – Jan 30 | Apr 10 – Apr 24 | — | — |
| Eggplant | Jan 16 – Jan 30 | Apr 10 – Apr 24 | — | — |
| Tomatoes | Jan 30 – Feb 13 | Apr 3 – Apr 17 | — | — |
| Lettuce | Jan 30 – Feb 13 | Mar 6 – Mar 20 | Feb 27 – Apr 3 | Sep 9 – Oct 7 |
| Kale | Jan 30 – Feb 13 | Feb 27 – Mar 13 | Feb 27 – Mar 13 | Aug 26 – Sep 16 |
| Broccoli | Jan 30 – Feb 13 | Mar 13 – Mar 27 | — | Jul 29 – Aug 19 |
| Cabbage | Jan 30 – Feb 13 | Mar 6 – Mar 20 | — | Jul 29 – Aug 19 |
| Cauliflower | Jan 30 – Feb 13 | Mar 13 – Mar 27 | — | Jul 29 – Aug 19 |
| Okra | Feb 13 – Feb 27 | Apr 17 – May 1 | Apr 17 – May 1 | — |
| Basil | Feb 13 – Feb 27 | Apr 3 – Apr 17 | — | — |
| Peas | — | — | Feb 13 – Mar 6 | Aug 12 – Sep 2 |
| Spinach | — | — | Feb 13 – Mar 6 | Sep 9 – Sep 30 |
| Radishes | — | — | Feb 20 – Apr 3 | Sep 23 – Oct 14 |
| Cucumbers | Feb 27 – Mar 6 | Apr 10 – Apr 17 | Apr 3 – Apr 17 | Aug 19 – Sep 2 |
| Zucchini & Summer Squash | Feb 27 – Mar 6 | — | Apr 3 – Apr 17 | Aug 26 – Sep 9 |
| Winter Squash & Pumpkins | Feb 27 – Mar 6 | — | Apr 3 – Apr 17 | — |
| Melons & Watermelon | Feb 27 – Mar 6 | Apr 10 – Apr 24 | — | — |
| Carrots | — | — | Mar 6 – Apr 3 | Aug 12 – Aug 26 |
| Beets | — | — | Mar 6 – Apr 3 | Aug 26 – Sep 9 |
| Potatoes | — | — | Mar 6 – Mar 27 | — |
| Swiss Chard | — | — | Mar 13 – Apr 10 | Aug 26 – Sep 9 |
| Cilantro | — | — | Mar 13 – Apr 3 | Sep 9 – Sep 30 |
| Green Beans | — | — | Apr 3 – Apr 24 | Aug 19 – Sep 2 |
| Sweet Corn | — | — | Apr 3 – Apr 17 | — |
| Sweet Potatoes | — | Apr 10 – May 1 | — | — |
| Garlic | — | — | — | Oct 21 – Nov 25 |
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 Mcnary Dam, WA weather station, 8 km away (elevation 361 ft (110 m)).
Frost dates near Plymouth
- Paterson Apr 14 · Oct 21
- Kennewick Mar 28 · Oct 30
- Benton City Apr 6 · Oct 24
- Richland Apr 6 · Oct 24
- Pasco Apr 27 · Oct 11
- Wallula Apr 7 · Oct 22
- West Richland Apr 6 · Oct 24
- Prosser Apr 14 · Oct 22
- Burbank Apr 7 · Oct 22
- Grandview May 1 · Oct 6
Frequently asked questions
When is the last frost in Plymouth, WA?
The median last spring frost in Plymouth, WA is March 27. There is still about a 10% chance of frost after April 14, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Plymouth, WA?
The median first fall frost is November 4, with about a 10% chance of frost before October 21.
How long is the growing season in Plymouth, WA?
About 222 days between the median last spring frost and first fall frost.
What planting zone is Plymouth, WA?
Plymouth, WA is in USDA hardiness zone 7b.