GreenlySeattle: frost dates
United States
In Seattle the last spring frost usually comes around 20 March and the first autumn frost around 24 November, which leaves about 249 frost-free days (median of 2016–2025). Tomato seedlings can go into open ground around 17 May.
| Last spring frost | around 20 March |
|---|---|
| First autumn frost | around 24 November |
| Frost-free days | 249 days |
Median of 2016–2025 for the 25 km grid cell of the city: the last day at or below 0 °C in spring and the first in autumn (ERA5 reanalysis via Open-Meteo). In a cold year a frost can come a week or two later — Greenly warns 48 hours ahead.
When to sow and plant
| Crop | Sow for seedlings | Plant out in a greenhouse | Open ground |
|---|---|---|---|
| Bell Pepper | 18 March | 31 May | 21 June |
| Chili Pepper | 26 March | 8 June | 29 June |
| Corn | — | 13 April | sow 4 May |
| Cucumber | 19 April | 31 May | 21 June |
| Eggplant | 22 March | 31 May | 21 June |
| Green Beans | 7 March | 13 April | 4 May |
| Melon | 9 April | 31 May | 21 June |
| Peas | — | 6 February | sow 27 February |
| Physalis | 12 March | 26 April | 17 May |
| Pumpkin | 20 March | 26 April | 17 May |
| Sweet Corn | — | 13 April | sow 4 May |
| Tomato | 28 February | 26 April | 17 May |
| Watermelon | 29 April | 31 May | 21 June |
| Zucchini | 25 March | 26 April | 17 May |
Planting out: a week after the last frost once the soil is warm enough for the crop; frost-hardy crops three weeks before it; an unheated greenhouse three weeks earlier. Seedlings are sown so they are ready on that day.
Seattle: weather for the next 7 days
Forecast by Open-Meteo. Nights at or below 0 °C are marked as frost.
Planted in autumn
| Crop | Plant around |
|---|---|
| Crocus | 25 October |
| Daffodil | 25 October |
| Garlic | 25 October |
| Hyacinth | 25 October |
| Lily | 25 October |
| Tulip | 25 October |
A month before the first autumn frost, so the roots grow before winter.