When to plant winter squash in Washington
Washington’s average last spring frost is April 20, and the first fall frost typically arrives around October 15 — about 178 frost-free days (USDA zones 4b, 5b, 6b, 7b, 8a, 8b, 9a). Winter Squash needs 80–110 days to mature, which fits comfortably within Washington's growing season.
Washington covers a wide range of climates, so your exact frost dates may differ from the state average by two weeks or more. For dates tuned to your town, use the calendar generator.
When to plant winter squash in Washington: the short answer
For a spring planting, plant out Apr 20 – May 7, with seeds started indoors Mar 23 – Apr 6. Wait until the soil is at least 60°F and frost is over.
Windows are ~1–2 week bands around each date. Frost dates are a statewide average from NOAA/NCEI normals; your town may differ by two weeks or more. Calendar year 2026.
How to grow winter squash in Washington, step by step
- Start seeds indoors (Mar 23 – Apr 6). Sow seeds 1 inch deep in seed-starting mix under bright light. They take 5-10 days to sprout, fastest in soil around 85°F. Harden seedlings off for a week before they go outside.
- Prepare the bed. It needs at least six to eight hours of direct sun a day and loose soil at least 18 inches deep, with a pH between 5.5 and 7.0. Dig in compost before planting.
- Plant out (Apr 20 – May 7). Space plants about 42 inches apart in rows 72 inches apart. It is killed by frost, so nothing goes outside until the danger has passed.
- Water and feed. Give it steady, even moisture, about an inch of water a week from rain or the hose.
- Watch for pests and problems. Pests: squash vine borer, squash bug, striped cucumber beetle. Diseases and disorders: powdery mildew, bacterial wilt.
- Harvest (from about Jul 16 – Aug 15). Winter Squash takes 80-110 days to reach harvest. Needs the whole season - direct sow only where you have 100+ frost-free days. Cure 10 days in warmth after harvest for storage.
Figures come from our crop data; dates use Washington’s average frost dates. More in the full winter squash growing guide.
Winter Squash planting dates by USDA zone in Washington
Washington spans USDA zones 4b, 5b, 6b, 7b, 8a, 8b, 9a. Colder zones, usually higher or further inland, have a later last spring frost and an earlier first fall frost than the state average, so the winter squash dates shift with them.
| Zone | Last frost | First frost | Season | Start indoors | Plant winter squash |
|---|---|---|---|---|---|
| Zone 4 | May 10 | Sep 25 | 135 days | Apr 12 – Apr 26 | May 10 – May 27 |
| Zone 5 | Apr 30 | Oct 5 | 160 days | Apr 2 – Apr 16 | Apr 30 – May 17 |
| Zone 6 | Apr 15 | Oct 15 | 185 days | Mar 18 – Apr 1 | Apr 15 – May 2 |
| Zone 7 | Apr 5 | Oct 25 | 200 days | Mar 8 – Mar 22 | Apr 5 – Apr 22 |
| Zone 8 | Mar 20 | Nov 5 | 230 days | Feb 20 – Mar 6 | Mar 20 – Apr 6 |
| Zone 9 | Feb 20 | Nov 30 | 280 days | Jan 23 – Feb 6 | Feb 20 – Mar 9 |
When to plant winter squash in nearby states
| State | Last frost | Plant out |
|---|---|---|
| Washington (this page) | April 20 | Apr 20 – May 7 |
| Oregon | April 20 | Apr 20 – May 7 |
Questions gardeners in Washington ask
When is the best time to plant winter squash in Washington?
Plant winter squash transplants outdoors in Washington between April 20 and May 7. That timing is set by Washington's average last spring frost of April 20; Washington spans several climates, so cooler and higher parts of the state run later.
When should I start winter squash seeds indoors in Washington?
Start seeds indoors between March 23 and April 6, about 3 weeks before the last frost, so the seedlings are ready to plant out from April 20.
What is the latest I can plant winter squash in Washington?
About July 27. Winter squash needs at least 80 days to mature, and frost around October 15 ends the season, so later plantings risk being cut short.
When will winter squash planted in Washington be ready to harvest?
Planted on time, winter squash is usually ready from about July 16 to August 15, 80-110 days after planting.
When is the last frost in Washington?
On average around April 20, with the first fall frost around October 15 - about 178 frost-free days. Your town may differ by two weeks or more.