USDA zone 9a in Washington
USDA plant hardiness zone 9a covers 19 locations across Washington (average annual extreme minimum 20 to 25 °F): Bainbridge Island, WA, Bay Center, WA, Edmonds, WA, Forks, WA, Friday Harbor, WA, Grayland, WA, and 13 more. Average last spring frost across this group ranges February 26 (Roche Harbor) to April 26 (Sekiu), and growing seasons run 177–276 days (Bay Center to Roche Harbor) — even within one state, because hardiness sets winter survival, not planting dates. The table below gives every Washington location's own frost dates; the printable planting calendar uses Kent, this group's median-season location.
- USDA zone
- 9a20 to 25 °F
- Last frost range
- Feb 26–Apr 26avg, 32°F
- First frost range
- Oct 17–Nov 29avg, 32°F
- Growing season range
- 177–276days
Locations in this group
Every location below shares this zone and a nearby weather station, but keeps its own frost dates — find your town for its own numbers, or use the ZIP planner on the home page for an instant personalized answer.
| Location | Also covers | Nearest station | Last frost | First frost | Season (days) |
|---|---|---|---|---|---|
| Bainbridge Island | Port Orchard, Suquamish, Manchester, Parkwood, Tracyton, Keyport | Bremerton | Mar 29 | Nov 14 | 227 |
| Bay Center | — | Raymond 2 S | Apr 26 | Oct 17 | 177 |
| Edmonds | Lynnwood, Port Gamble Tribal Community, North Lynnwood, Lake Stickney, Alderwood Manor | Everett Snohomish Ap | Mar 9 | Nov 17 | 250 |
| Forks | Neah Bay, Sekiu | Quillayute State Ap | Apr 20 | Oct 26 | 190 |
| Friday Harbor | — | Friday Harbor Ap | Mar 26 | Nov 10 | 230 |
| Grayland | — | Grayland | Mar 29 | Nov 7 | 224 |
| Kent * | Renton | Kent | Mar 20 | Nov 10 | 233 |
| Marrowstone | — | Port Townsend | Mar 1 | Nov 28 | 274 |
| North Bonneville | — | Bonneville Dam | Mar 14 | Nov 27 | 257 |
| Ocean | Moclips, Pacific Beach | Humptulips Salmon Hatchery | Apr 26 | Oct 22 | 180 |
| Ocean Park | Ilwaco, Long Beach | Long Beach Exp Stn | Apr 6 | Oct 26 | 200 |
| Ocean Shores | Westport | Hoquiam Bowerman Ap | Mar 30 | Nov 14 | 228 |
| Renton | Mercer Island, Boulevard Park | Renton Muni Ap | Mar 13 | Nov 16 | 248 |
| Roche Harbor | Friday Harbor | Olga 2 Se | Feb 26 | Nov 29 | 276 |
| Seattle | Bellevue, Kirkland, Shoreline, Mercer Island, Kenmore, Indianola, +3 more | Seattle Sand Pt Wsfo | Mar 8 | Nov 23 | 259 |
| Seattle | Vashon, Renton, SeaTac, Burien, Tukwila, Des Moines, +1 more | Seattle Tacoma Intl Ap | Mar 2 | Nov 23 | 266 |
| Sekiu | — | Forks 1 E | Apr 26 | Oct 25 | 182 |
| Tacoma | — | Tacoma #1 | Mar 8 | Nov 14 | 250 |
| Tacoma | Artondale, Fox Island | Tacoma Narrows Ap | Mar 11 | Nov 21 | 254 |
* Kent is this group's median-season location — the calendar below is computed from its data.
Data: NOAA NCEI U.S. Climate Normals 1991–2020 (public domain) and USDA Plant Hardiness Zone Map 2023. Planting windows synthesized from U.S. Cooperative Extension guides.
Planting calendar (Kent, representative)
Computed from Kent's average frost dates — the median-season location in this Washingtonzone 9a group. hatched = start seeds indoors, solid green = plant out, teal = a fall sowing, and the terracotta dot marks the estimated first harvest. Ranges are extension-guide planning guidance, not guarantees — your own location's dates may run a week or two earlier or later (see the table above).
- Start indoors
- Plant out
- Fall sowing
- First harvest
| Crop | Frost tolerance | Start indoors | Plant out | First harvest | Fall planting | Season fit |
|---|---|---|---|---|---|---|
| Tomato | Tender | Jan 23 – Feb 6 | Mar 27 – Apr 3 | May 26 – Jun 15 | — | matures comfortably |
| Pepper | Very tender | Jan 9 – Jan 23 | Apr 3 – Apr 10 | Jun 2 – Jul 2 | — | matures comfortably |
| Cucumber | Tender | Feb 20 – Feb 27 | Mar 27 – Apr 3 | May 16 – Jun 5 | — | matures comfortably |
| Summer squash / zucchini | Tender | — | Mar 27 – Apr 3 | May 11 – May 26 | — | matures comfortably |
| Bush bean | Tender | — | Mar 27 – Apr 3 | May 16 – May 26 | Sep 11 – Sep 21 | matures comfortably |
| Sweet corn | Tender | — | Mar 20 – Apr 3 | May 19 – Jun 18 | — | matures comfortably |
| Basil | Very tender | Feb 6 – Feb 20 | Mar 27 – Apr 3 | Apr 26 – May 11 | — | matures comfortably |
| Lettuce | Half-hardy | Feb 6 – Feb 20 | Feb 20 – Mar 6 | Apr 6 – Apr 21 | Aug 28 – Sep 12 | matures comfortably |
| Pea | Hardy | — | Feb 6 – Feb 20 | Apr 2 – Apr 17 | Aug 18 – Sep 2 | matures comfortably |
| Spinach | Hardy | — | Feb 6 – Feb 20 | Mar 18 – Mar 28 | Sep 7 – Sep 17 | matures comfortably |
| Carrot | Half-hardy | — | Feb 27 – Mar 6 | Apr 28 – May 18 | Aug 8 – Aug 28 | matures comfortably |
| Broccoli | Half-hardy | Jan 23 – Feb 6 | Feb 20 – Mar 6 | Apr 16 – May 6 | Aug 13 – Sep 2 | matures comfortably |
Which crops fit this growing season
Using Kent's own 233-day growing season (32°F, NOAA 1991–2020 median) against each crop's real days-to-maturity range: 12 of 12 crops mature here with comfortable margin. A different location in the table above with a longer or shorter season will get a different mix — the ZIP planner on the home page gives your own.
Frost & freeze dates (Kent)
From NOAA's 1991–2020 Climate Normals at station USC00454169. The median (p50) is the average date; the 90%-safe column is the date the freeze has passed in about 9 years out of 10 — the conservative date to plant after or harvest before.
| Threshold | Last spring — avg | Last spring — 90%-safe | First fall — avg | First fall — 90%-safe | Season (days) |
|---|---|---|---|---|---|
| 36°F | Apr 11 | Apr 30 | Oct 27 | Nov 11 | 197 |
| 32°F (freeze) | Mar 20 | Apr 8 | Nov 10 | Nov 26 | 233 |
| 28°F | Feb 25 | Mar 16 | Nov 24 | Dec 20 | 275 |
| 24°F | Jan 24 | Feb 27 | Dec 8 | Jan 17 | 326 |
Growing degree days
Growing degree days (GDD) accumulate warmth above a base temperature over the year — a better predictor of crop development than the calendar alone. This group's median GDD (base 50°F) across all 19 locations is 1,712; Kent's own reading is shown below.
| Model | °F·days | Used for |
|---|---|---|
| Base 50°F (warm-season) | 2,408 | standard warm-season base (tomato, corn, beans) |
| Base 40°F (cool-season) | 5,185 | cool-season crops (brassicas, greens) |
Hardiness zone 9a in Washington
Zone 9a means an average annual extreme minimum winter temperature of about 20 to 25 °F on the USDA's 2023 map — the number that tells you which perennials, shrubs, and trees reliably survive an average winter here. It does not set your planting dates, which come from the frost calendar above. Washington spans 8 hardiness zones in this dataset — see all Washington locations for the full range, including zones6a, 6b, 7a, 7b, 8a, 8b, 9b.
Explore zone 9a in other states at zone 9a, or see all USDA hardiness zones.
Frequently asked questions
- What does USDA hardiness zone 9a mean in Washington?
- Zone 9a means an average annual extreme minimum winter temperature of 20 to 25 °F — the standard USDA measure of which perennials survive winter. 19 locations in Washington fall in this zone. It does not set planting dates; see the frost calendar below for that.
- Where in Washington's zone 9a is the growing season longest?
- Roche Harbor runs the longest season on this page at about 276 days; Bay Center is shortest at about 177 days — they share the same hardiness zone, but they sit at different weather stations, so their frost calendars differ.
- When should I plant tomatoes in Washington's zone 9a?
- Using Kent's frost dates (this page's median-season location): start seeds indoors about Jan 23 – Feb 6, then transplant outside about Mar 27 – Apr 3. Your own location in the table above may differ by a week or two — use the ZIP planner on the home page for your exact station's dates.
- Does every location in Washington's zone 9a have the same frost dates?
- No — they do not all share a weather station, so frost dates vary by a week or more across the 19 locations listed (see the table above for each location's own dates).
Sources & method
Frost, freeze, growing-season, and growing-degree-day figures are NOAA NCEI U.S. Climate Normals 1991–2020, one reading per location's own nearest station (see the table above). The hardiness zone is the USDA Plant Hardiness Zone Map 2023, matched to each location's ZIP. Planting windows are computed by counting from the average last and first frost using per-crop offsets synthesized from U.S. Cooperative Extension guides — the full method and citations are on the methodology page.