Seattle, WA Frost Dates & Growing Season

The two dates every Seattle garden is planned around, plus ready-computed planting windows for the most popular crops.

Last spring frost
Mar 13
~50% chance of frost after
First fall frost
Nov 17
~50% chance of frost before
Growing season
249 days
frost-free stretch
USDA zone
9a
2023 hardiness map
Risky (1 year in 10)MedianSafe (9 years in 10)
Last spring frost Feb 20 Mar 13 Apr 1
First fall frost Dec 6 Nov 17 Nov 1
Hard freeze (28°F), median last Feb 18 · first Dec 2

Computed from NOAA 1991–2020 climate normals at the Seattle Boeing Field station (9 km from central Seattle). "Safe" means frost past that date happens only about one year in ten. Your exact garden can still run days either way with elevation and terrain — check your own ZIP with the frost date lookup.

Planting windows for Seattle

Computed from Seattle's own frost dates. Click any crop for the full zone-9 growing guide — varieties, spacing, fall plantings, and more.

CropStart seeds indoorsTransplantDirect sow
🍅 Tomatoes Jan 16 – Jan 30 Mar 20 – Mar 27
🫑 Peppers Jan 2 – Jan 16 Mar 27 – Apr 3
🥬 Lettuce Jan 30 – Feb 13 Feb 13 – Feb 27 Feb 13 – Mar 13
🫛 Peas Jan 30 – Feb 13
🥕 Carrots Feb 20 – Mar 13
🥦 Broccoli Jan 23 – Feb 6 Feb 20 – Mar 6
🥬 Kale Jan 30 – Feb 13 Feb 13 – Feb 27 Feb 13 – Feb 27
🥒 Cucumbers Feb 13 – Feb 20 Mar 20 – Mar 27 Mar 20 – Mar 27
🥒 Zucchini Feb 13 – Feb 20 Mar 20 – Mar 27 Mar 20 – Mar 27
🫘 Green Beans (Bush) Mar 20 – Mar 27
🌽 Sweet Corn Mar 20 – Mar 27
🌿 Basil Jan 30 – Feb 13 Mar 20 – Mar 27 Mar 27 – Apr 3
🧄 Garlic Fall: Oct 6 – Nov 3

Want this for all 50 crops, or as a printable seed-shelf schedule? Use the planting calendar and the seed starting scheduler — both can use Seattle's dates automatically after a lookup.

Reading the season in Seattle

With roughly 249 frost-free days, Seattle gardens fit long-season crops — melons, winter squash, sweet potatoes — with room left for spring and fall rounds of greens and roots. The first frost around Nov 17 is late enough that fall planting is a full second season, not an afterthought.

Frequently asked questions

When is the last frost in Seattle, WA?

The average last spring frost in Seattle is around Mar 13, based on 1991–2020 climate normals. That's a median — about half of years see a later frost, so tender crops are safest going out a week or two after this date.

When is the first frost in Seattle, WA?

The average first fall frost in Seattle arrives around Nov 17. Crops still in the garden need to mature before then, and frost-tender plants need harvesting or protection as the date approaches.

How long is the growing season in Seattle?

About 249 frost-free days on average, from Mar 13 to Nov 17. That comfortably fits long-season crops like melons and winter squash, plus spring and fall plantings of cool-season vegetables.

What USDA zone is Seattle in?

USDA zone 9a on the 2023 Plant Hardiness Zone Map. Note that zones describe winter cold, not frost timing — these frost dates are the numbers to plan plantings around.