Frost dates for 98178 — Seattle, WA
How Seattle compares
- In 8 years out of 10, the last spring frost in Seattle falls between February 19 and March 31, a 40-day window. The first fall frost falls between October 29 and December 9.
- The median last frost is 39 days earlier than the Washington median of Apr 21.
- Its 248-day growing season is longer than 89% of the 491 Washington places with a regular frost season (state median 182 days).
- The last frost is 10 days later than the zone 9a median of Mar 3. Hardiness zones measure winter cold, not season length, so use these dates rather than a zone 9a chart.
- The weather station records an average of 30 nights a year at or below 32°F.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | February 19 |
| 50% (median) | March 13 |
| 10% (safe for tender plants) | March 31 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | October 29 |
| 50% (median) | November 16 |
| 90% (late) | December 9 |
Frost here means 32°F (0°C). A median date means half of years have their last frost earlier and half later.
Planting calendar for Seattle, WA
Frost dates for 98178 — Seattle, WA — last frost Mar 13, first frost Nov 16, zone 9a. whenisthelastfrost.com
When to plant vegetables in Seattle, WA
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Dec 19 – Jan 2 | Feb 13 – Feb 27 | — | — |
| Peppers | Jan 2 – Jan 16 | Mar 27 – Apr 10 | — | — |
| Eggplant | Jan 2 – Jan 16 | Mar 27 – Apr 10 | — | — |
| Tomatoes | Jan 16 – Jan 30 | Mar 20 – Apr 3 | — | — |
| Lettuce | Jan 16 – Jan 30 | Feb 20 – Mar 6 | Feb 13 – Mar 20 | Sep 21 – Oct 19 |
| Kale | Jan 16 – Jan 30 | Feb 13 – Feb 27 | Feb 13 – Feb 27 | Sep 7 – Sep 28 |
| Broccoli | Jan 16 – Jan 30 | Feb 27 – Mar 13 | — | Aug 10 – Aug 31 |
| Cabbage | Jan 16 – Jan 30 | Feb 20 – Mar 6 | — | Aug 10 – Aug 31 |
| Cauliflower | Jan 16 – Jan 30 | Feb 27 – Mar 13 | — | Aug 10 – Aug 31 |
| Okra | Jan 30 – Feb 13 | Apr 3 – Apr 17 | Apr 3 – Apr 17 | — |
| Basil | Jan 30 – Feb 13 | Mar 20 – Apr 3 | — | — |
| Peas | — | — | Jan 30 – Feb 20 | Aug 24 – Sep 14 |
| Spinach | — | — | Jan 30 – Feb 20 | Sep 21 – Oct 12 |
| Radishes | — | — | Feb 6 – Mar 20 | Oct 5 – Oct 26 |
| Cucumbers | Feb 13 – Feb 20 | Mar 27 – Apr 3 | Mar 20 – Apr 3 | Aug 31 – Sep 14 |
| Zucchini & Summer Squash | Feb 13 – Feb 20 | — | Mar 20 – Apr 3 | Sep 7 – Sep 21 |
| Winter Squash & Pumpkins | Feb 13 – Feb 20 | — | Mar 20 – Apr 3 | — |
| Melons & Watermelon | Feb 13 – Feb 20 | Mar 27 – Apr 10 | — | — |
| Carrots | — | — | Feb 20 – Mar 20 | Aug 24 – Sep 7 |
| Beets | — | — | Feb 20 – Mar 20 | Sep 7 – Sep 21 |
| Potatoes | — | — | Feb 20 – Mar 13 | — |
| Swiss Chard | — | — | Feb 27 – Mar 27 | Sep 7 – Sep 21 |
| Cilantro | — | — | Feb 27 – Mar 20 | Sep 21 – Oct 12 |
| Green Beans | — | — | Mar 20 – Apr 10 | Aug 31 – Sep 14 |
| Sweet Corn | — | — | Mar 20 – Apr 3 | — |
| Sweet Potatoes | — | Mar 27 – Apr 17 | — | — |
| Garlic | — | — | — | Nov 2 – Dec 7 |
Dates come from the median frost dates and common extension-service timing. Adjust for your soil temperature, microclimate and the varieties you grow.
About these dates
Based on 1991–2020 NOAA climate normals for the Renton Muni Ap, WA weather station, 2 km away (elevation 30 ft (9 m)).
ZIP codes in Seattle: 98101 98102 98103 98104 98105 98106 98107 98108 98109 98111 98112 98113 98114 98115 98116 98117 98118 98119 98121 98122 98124 98125 98126 98127 98129 98131 98133 98134 98136 98138 98139 98141 98144 98145 98146 98148 98154 98155 98158 98160 98161 98164 98165 98166 98168 98170 98174 98175 98177 98178 98181 98185 98188 98190 98191 98194 98195 98198 98199
Frost dates near Seattle
- Renton Mar 13 · Nov 16
- Mercer Island Mar 13 · Nov 17
- Seahurst Mar 2 · Nov 23
- Kent Mar 20 · Nov 10
- Bellevue Mar 8 · Nov 23
- Medina Mar 8 · Nov 23
- Issaquah Mar 30 · Nov 7
- Maple Valley Apr 20 · Oct 25
Frequently asked questions
When is the last frost in Seattle, WA?
The median last spring frost in Seattle, WA is March 13. There is still about a 10% chance of frost after March 31, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Seattle, WA?
The median first fall frost is November 16, with about a 10% chance of frost before October 29.
How long is the growing season in Seattle, WA?
About 248 days between the median last spring frost and first fall frost.
What planting zone is Seattle, WA?
Seattle, WA is in USDA hardiness zone 9a.