Seattle, Washington: planting zone & frost dates
Seattle is in USDA plant hardiness zone 9a, where the average coldest winter night reaches 20 to 25°F (-6.7 to -3.9°C). The typical last spring frost is around Mar 16 and the first fall frost around Nov 15.
Frost dates
| Probability | Last spring frost (32°F) | First fall frost (32°F) |
|---|---|---|
| Safer (10% risk) | Mar 29 | Nov 4 |
| Typical planning date (30% risk) | Mar 16 | Nov 15 |
| Median (50%) | Mar 8 | Nov 23 |
How to read this: after the spring "10% risk" date, a 32°F frost happens in only about 1 year in 10. In fall, the "10% risk" date is the early end — a frost before it happens about 1 year in 10.
Frost data comes from NOAA station SEATTLE SAND PT WSFO, WA (USW00094290), 6.5 mi (10.4 km) from the city center and 85 ft lower than the city center (-26 m). Record used for the 1991–2020 normals: 29 years.
Why your yard may differ from the station: microclimates.
Hardiness zone across Seattle
All 31 ZIP codes covering Seattle are in zone 9a.
ZIP codes in Seattle and their zones
| ZIP | Zone | Share of city land |
|---|---|---|
| 98115 | 9a | 7.8% |
| 98118 | 9a | 7.4% |
| 98108 | 9a | 7.3% |
| 98125 | 9a | 6.5% |
| 98106 | 9a | 6.2% |
| 98103 | 9a | 5.5% |
| 98199 | 9a | 5.1% |
| 98105 | 9a | 4.6% |
| 98117 | 9a | 4.6% |
| 98134 | 9a | 4.0% |
| 98144 | 9a | 4.0% |
| 98112 | 9a | 3.8% |
| 98116 | 9a | 3.6% |
| 98126 | 9a | 3.6% |
| 98133 | 9a | 3.5% |
| 98119 | 9a | 2.9% |
| 98122 | 9a | 2.8% |
| 98136 | 9a | 2.7% |
| 98107 | 9a | 2.6% |
| 98177 | 9a | 2.6% |
| 98109 | 9a | 2.3% |
| 98102 | 9a | 1.5% |
| 98178 | 9a | 1.3% |
| 98104 | 9a | 1.1% |
| 98146 | 9a | 1.1% |
| 98101 | 9a | 0.6% |
| 98121 | 9a | 0.5% |
| 98195 | 9a | 0.5% |
| 98154 | 9a | 0.0% |
| 98164 | 9a | 0.0% |
| 98174 | 9a | 0.0% |
Vegetable planting calendar for Seattle
Dates are counted from the 30%-risk frost dates above (last frost Mar 16, first frost Nov 15). Shift a week later in cold spots or low-lying ground.
| Crop | Start indoors | Transplant / plant out | Direct sow | Fall crop sow/plant |
|---|---|---|---|---|
| Tomato | Jan 19 – Feb 2 | Mar 23 – Apr 6 | — | — |
| Pepper | Jan 5 – Jan 19 | Mar 30 – Apr 13 | — | — |
| Lettuce | Feb 2 – Feb 16 | Mar 2 – Mar 23 | Feb 16 – Mar 30 | Sep 6 – Oct 4 |
| Green Beans | — | — | Mar 23 – Apr 27 | Aug 23 – Sep 6 |
| Sweet Corn | — | — | Mar 23 – Apr 20 | — |
| Zucchini & Summer Squash | Feb 16 – Feb 23 | Mar 23 – Apr 6 | Mar 23 – Apr 13 | Aug 23 – Sep 6 |
| Cucumber | Feb 16 – Feb 23 | Mar 30 – Apr 6 | Mar 23 – Apr 13 | Aug 23 – Sep 6 |
| Carrot | — | — | Feb 23 – Mar 30 | Aug 23 – Sep 6 |
| Onion | Dec 22 – Jan 5 | Feb 16 – Mar 2 | — | — |
| Potato | — | Feb 16 – Mar 9 | — | — |
| Basil | Feb 2 – Feb 16 | Mar 30 – Apr 13 | Mar 30 – Apr 20 | — |
| Spinach | — | — | Feb 2 – Mar 2 | Sep 20 – Oct 18 |
| Kale | Jan 19 – Feb 2 | Feb 16 – Mar 9 | Feb 16 – Mar 9 | Sep 6 – Oct 4 |
| Broccoli | Jan 19 – Feb 2 | Mar 2 – Mar 23 | — | Aug 23 – Sep 6 |
| Peas | — | — | Feb 2 – Feb 23 | Sep 6 – Sep 20 |
| Eggplant | Jan 5 – Jan 19 | Mar 30 – Apr 13 | — | — |
| Cabbage | Jan 19 – Feb 2 | Feb 16 – Mar 2 | — | Aug 23 – Sep 6 |
| Radish | — | — | Feb 9 – Mar 30 | Oct 4 – Nov 1 |
| Strawberry | — | Feb 16 – Mar 9 | — | — |
| Beets | — | — | Feb 23 – Apr 6 | Sep 6 – Sep 20 |
Nearby cities in Washington
- Kirkland — zone 9a, last frost Mar 16, first frost Nov 15
- Bellevue — zone 8b, last frost Mar 16, first frost Nov 15
- Renton — zone 9a, last frost Mar 22, first frost Nov 7
- Redmond — zone 8b, last frost Mar 16, first frost Nov 15
- Kent — zone 8b, last frost Mar 29, first frost Nov 3
- Federal Way — zone 8b, last frost Mar 17, first frost Nov 7
More: all Washington cities · other zone 9a cities: San Antonio, TX, Austin, TX, Las Vegas, NV, Portland, OR, Tucson, AZ, Baton Rouge, LA, Tallahassee, FL, Mobile, AL
Seattle gardening questions
When is the last frost in Seattle, WA?
Plan around Mar 16. At NOAA's Seattle Sand Pt WSFO, WA station, 6.5 mi from the city center, there is a 30% chance of a 32°F frost after that date. Half of springs have their last frost by Mar 8, and after Mar 29 the risk drops to about 1 in 10. A hard freeze (28°F) usually ends earlier, around Feb 11. The 90% and 10% dates are 44 days apart, close to the 36-day median for cities on this site.
When should I plant tomatoes in Seattle, WA?
Start seeds indoors Jan 19 – Feb 2 and set transplants outside Mar 23 – Apr 6, once nights stay above 50°F and the soil is near 60°F. That leaves 244 days between the 30% frost dates, enough for most varieties including 80–85-day slicers. More: tomato planting dates by zone.
How long is the growing season in Seattle?
About 259 days without a 32°F frost in a typical (median) year. In 9 years out of 10 the season lasts at least 231 days, and in 1 year in 10 it runs 289 days or more. In fall there is a 10% chance of frost by Nov 4 and a 30% chance by Nov 15. That is the longest of the 18 Washington cities on this site.
When should I plant a fall garden in Seattle?
Count back from the first fall frost (Nov 15): transplant broccoli Aug 23 – Sep 6; sow kale Sep 6 – Oct 4; sow lettuce Sep 6 – Oct 4; sow radishes Oct 4 – Nov 1. Hardy crops keep growing through light frosts; the median 28°F hard freeze here is Dec 11. How the math works: succession and fall planting.
Did Seattle's hardiness zone change on the 2023 map?
Yes. Most of Seattle was zone 8b on the 2012 map and is zone 9a on the 2023 map — half a zone warmer, like about 56% of U.S. ZIP codes. The shift comes from a newer 1991–2020 averaging period plus more weather stations and better mapping; it does not mean last frost comes earlier. Why the 2023 map is warmer.
How does Seattle compare with Renton, WA?
Both are in zone 9a. The typical last spring frost in Seattle (Mar 16) comes about 6 days earlier than in Renton, WA (Mar 22), 12 miles away, and the first fall frost is Nov 15 versus Nov 7. The two cities use different NOAA stations.