USDA hardiness zone lookup
Seattle, WA — USDA Zone 9a
Seattle, Washington · 248-day growing season
Frost dates and growing season in Seattle
| USDA hardiness zone | Zone 9a |
|---|---|
| Average last spring frost | March 14 |
| Average first fall frost | November 17 |
| Growing season length | ~248 days |
| Temperature range (F) | 20 to 30°F |
| Temperature range (C) | -7 to -1°C |
Seattle spans USDA zones 8 to 9 across its ZIP codes (Zone 8b, Zone 9a); the city center sits in Zone 9a, so warmer and cooler pockets exist either side of that.
These are 50%-probability averages modeled from Seattle's USDA hardiness zone and regional climate normals — not a single-station reading. In a typical year the last spring frost will have passed by March 14, but a colder-than-average year can run 1-2 weeks later. Plant tender crops (tomatoes, peppers, basil) once both soil and night temperatures are consistently warm — a thermometer beats the calendar.
Growing season in Seattle
Seattle, Washington sits in USDA Zone 9a, with roughly 248 frost-free days between an average last spring frost around March 14 and a first fall frost around November 17. That is a near year-round season — the limiting factor is summer heat, not frost, so schedule cool-season crops for winter and protect tender ones from extreme highs. Seattle lies near 47.6°N; higher-latitude gardens get longer midsummer days but a tighter shoulder season at this zone. As a large metro, the built-up core typically runs up to half a zone warmer than outlying suburbs through the urban heat-island effect — sheltered city gardens often push tender crops a little earlier than the average suggests.
What grows in Seattle
Seattle falls in USDA Zone 9a, so the same hardiness constraints apply as the full Zone 9 guide. Vegetables, herbs, and fruit trees rated to Zone 9a (or hardier) will overwinter here in a typical year.
- Tomatoes (year-round in many areas)
- Peppers (all year)
- Citrus (oranges, lemons, limes, grapefruit)
- Avocado
- Mango (warmer areas)
- Banana
- Sweet potatoes
- Okra
- Southern peas
- Pomegranates
What to plant in Seattle this week
Seattle is in high summer — most spring plantings are in. Keep an eye on watering and start planning your fall crop. Cool-season seedlings (broccoli, cabbage, lettuce) can be started indoors for a fall transplant.
- When to plant tomatoes in zone 9
- When to plant peppers in zone 9
- When to plant bush beans in zone 9
- When to plant cucumbers in zone 9
- When to plant basil in zone 9
Full planting calendar for Seattle
Crop-by-crop sowing, transplant, and harvest dates calibrated to zone 9 averages:
- When to plant tomatoes in zone 9
- When to plant peppers in zone 9
- When to plant basil in zone 9
- When to plant garlic in zone 9
- When to plant lettuce in zone 9
- When to plant bush beans in zone 9
- When to plant cucumbers in zone 9
- When to plant summer squash in zone 9
- When to plant peas in zone 9
- When to plant carrots in zone 9
ZIP codes in Seattle
Drill down to the precise frost window and planting calendar for a specific ZIP in Seattle:
- 98101 — Seattle (Zone 9a)
- 98109 — Seattle (Queen Anne) (Zone 9a)
- 98103 — Seattle (Fremont) (Zone 8b)
- 98105 — Seattle (University District) (Zone 9a)
- 98115 — Seattle (Wedgwood) (Zone 9a)
- 98118 — Seattle (Columbia City) (Zone 9a)
- 98125 — Seattle (Lake City) (Zone 8b)
- 98133 — Seattle (Bitter Lake) (Zone 8b)
Local microclimate notes
Zone tables give you the average — but Seattlegardens vary. South-facing walls and paved areas can run a full half-zone warmer than the published rating. Low-lying spots, frost pockets, and shaded north sides can run colder. If you've gardened here a few seasons, your own frost record — the last time you actually got frost damage — beats any national average.
Source and methodology
Hardiness zone from the USDA Plant Hardiness Zone Map (2023 revision). Frost-date and growing-season figures are modeled from Seattle's USDA hardiness zone and regional NOAA 1991-2020 climate normals — zone-level estimates, not a per-station record, so treat them as planning guidance and confirm against your own local frost history. Crop recommendations draw on US Cooperative Extension references, curated by the Growli editorial team. Last reviewed June 2026.
Other cities in Washington
- Bellevue, WA — USDA Zone 8b
- Bellingham, WA — USDA Zone 8b
- Bothell, WA — USDA Zone 8b
- Ellensburg, WA — USDA Zone 6b
- Everett, WA — USDA Zone 8b
- Federal Way, WA — USDA Zone 8b
- Kennewick, WA — USDA Zone 7a
- Kent, WA — USDA Zone 8b
- Kirkland, WA — USDA Zone 8b
- Marysville, WA — USDA Zone 8b
- Moses Lake, WA — USDA Zone 6b
- Olympia, WA — USDA Zone 8b
- All of Washington by zone