Seattle is now generally classified as USDA planting (hardiness) zone 9a under the latest 2023 USDA map, though many older or local references still describe it as zone 8b.

Quick Scoop 🌱

  • Most up‑to‑date USDA designation: Zone 9a (average annual minimum 20–25°F / about −6.7 to −3.9°C).
  • Older maps & some gardening sites: Zone 8b (15–20°F minimums).
  • Reality on the ground: Many gardeners still choose plants rated zone 8b or colder because occasional cold snaps can drop below what 9a suggests.

Why the Confusion?

  • In 2023, USDA updated the hardiness map using 1991–2020 data, which nudged much of western Washington, including Seattle, one half‑zone warmer (from 8b to 9a).
  • Some gardening blogs and guides haven’t fully updated yet and still list Seattle as 8b.

What This Means For Your Garden

  • You can grow a wider range of heat‑loving crops (tomatoes, peppers, eggplants, some melons) more reliably than in past decades.
  • It’s still smart to:
    • Favor plants hardy to at least zone 8b.
    • Watch for microclimates (exposed hillsides may feel more like 8b; sheltered urban spots can behave closer to a warm 9a).

TL;DR: If a form or catalog asks “what planting zone is Seattle?” the safest, current answer is USDA zone 9a , but shop and plan like a cautious 8b/9a gardener to handle occasional cold swings.

Information gathered from public forums or data available on the internet and portrayed here.