When to Plant Onions in Washington
In Washington, the time to plant onions outside runs from Feb 2 – Feb 16 in Burien to Apr 8 – Apr 22 in Pullman. In Seattle, it's Feb 8 – Feb 22. The average last spring frost differs by about 9 weeks across the state (Mar 2 in Burien, May 6 in Pullman), so use the dates for the town nearest you.
Onions are cold-hardy. Plant sets or transplants early so they grow leaves before long summer days trigger bulbing.
- Start indoors: 10–12 weeks before the last frost.
- Plant outside: 2–4 weeks before the last frost.
Onions planting dates in Washington by city
| City | Zone | Start indoors | Plant outside |
|---|---|---|---|
| Auburn | 8b | Dec 26 – Jan 9 | Feb 20 – Mar 6 |
| Bellevue | 9a | Dec 14 – Dec 28 | Feb 8 – Feb 22 |
| Bellingham | 8b | Jan 7 – Jan 21 | Mar 4 – Mar 18 |
| Bothell | 8b | Dec 14 – Dec 28 | Feb 8 – Feb 22 |
| Bremerton | 8b | Jan 4 – Jan 18 | Mar 1 – Mar 15 |
| Burien | 9a | Dec 8 – Dec 22 | Feb 2 – Feb 16 |
| Des Moines | 9a | Dec 8 – Dec 22 | Feb 2 – Feb 16 |
| Edmonds | 9a | Dec 15 – Dec 29 | Feb 9 – Feb 23 |
| Everett | 8b | Dec 30 – Jan 13 | Feb 24 – Mar 10 |
| Federal Way | 8b | Dec 14 – Dec 28 | Feb 8 – Feb 22 |
| Issaquah | 8b | Dec 19 – Jan 2 | Feb 13 – Feb 27 |
| Kennewick | 7b | Jan 3 – Jan 17 | Feb 28 – Mar 14 |
| Kent | 8b | Dec 26 – Jan 9 | Feb 20 – Mar 6 |
| Kirkland | 9a | Dec 14 – Dec 28 | Feb 8 – Feb 22 |
| Lacey | 8b | Feb 4 – Feb 18 | Apr 1 – Apr 15 |
| Lake Stevens | 8b | Dec 30 – Jan 13 | Feb 24 – Mar 10 |
| Lakewood | 8b | Dec 17 – Dec 31 | Feb 11 – Feb 25 |
| Longview | 8b | Jan 14 – Jan 28 | Mar 11 – Mar 25 |
| Lynnwood | 9a | Dec 15 – Dec 29 | Feb 9 – Feb 23 |
| Marysville | 8b | Dec 30 – Jan 13 | Feb 24 – Mar 10 |
| Mount Vernon | 8b | Dec 30 – Jan 13 | Feb 24 – Mar 10 |
| Olympia | 8b | Feb 4 – Feb 18 | Apr 1 – Apr 15 |
| Pasco | 7b | Feb 2 – Feb 16 | Mar 30 – Apr 13 |
| Pullman | 6b | Feb 11 – Feb 25 | Apr 8 – Apr 22 |
| Puyallup | 8b | Jan 17 – Jan 31 | Mar 14 – Mar 28 |
| Redmond | 8b | Dec 14 – Dec 28 | Feb 8 – Feb 22 |
| Renton | 9a | Dec 19 – Jan 2 | Feb 13 – Feb 27 |
| Richland | 7b | Jan 12 – Jan 26 | Mar 9 – Mar 23 |
| Sammamish | 8b | Jan 5 – Jan 19 | Mar 2 – Mar 16 |
| SeaTac | 9a | Dec 8 – Dec 22 | Feb 2 – Feb 16 |
| Seattle | 9a | Dec 14 – Dec 28 | Feb 8 – Feb 22 |
| Shoreline | 9a | Dec 14 – Dec 28 | Feb 8 – Feb 22 |
| Spokane | 7a | Feb 1 – Feb 15 | Mar 29 – Apr 12 |
| Spokane Valley | 7a | Feb 1 – Feb 15 | Mar 29 – Apr 12 |
| Tacoma | 8b | Dec 14 – Dec 28 | Feb 8 – Feb 22 |
| University Place | 8b | Dec 17 – Dec 31 | Feb 11 – Feb 25 |
| Vancouver | 8b | Jan 4 – Jan 18 | Mar 1 – Mar 15 |
| Walla Walla | 7a | Jan 2 – Jan 16 | Feb 27 – Mar 13 |
| Wenatchee | 7a | Jan 10 – Jan 24 | Mar 7 – Mar 21 |
| Yakima | 7a | Jan 14 – Jan 28 | Mar 11 – Mar 25 |
Calculated from each town's average (50%) frost dates, from the nearest NOAA station (1991–2020). Typical dates for the 2027 planting season, based on NOAA's 1991–2020 averages. They are long-term odds, not a forecast: always check your local forecast before planting. Zones: 2023 USDA Plant Hardiness Zone Map (USDA-ARS and Oregon State University). Not the official map; see planthardiness.ars.usda.gov.
See all frost dates in Washington, or the general guide to when to plant onions.
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