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 |
|---|---|---|---|
| Achocha | 18 February | 30 March | 20 April |
| Arugula | — | 6 February | sow 27 February |
| Basil | 23 April | 31 May | 21 June |
| Beet | — | 6 February | sow 27 February |
| Bell Pepper | 18 March | 31 May | 21 June |
| Black-eyed Susan | 17 February | — | 20 April |
| Bok Choy | 23 February | 30 March | 20 April |
| Broad bean | — | 6 February | sow 27 February |
| Broccoli | — | 6 February | sow 27 February |
| Brussels Sprouts | 23 December | 6 February | 27 February |
| Cabbage | — | 6 February | sow 27 February |
| Calendula | — | 6 February | sow 27 February |
| Carrot | — | — | sow 27 February |
| Cauliflower | 26 December | 6 February | 27 February |
| Celeriac | 12 January | 30 March | 20 April |
| Celery | 12 January | 30 March | 20 April |
| Celosia | 23 March | 7 May | 28 May |
| Chamomile | — | 6 February | sow 27 February |
| Chayote | 15 January | 13 April | 4 May |
| Chickpea | — | — | sow 27 February |
| Chili Pepper | 26 March | 8 June | 29 June |
| China aster | 9 April | 31 May | 21 June |
| Chives | — | — | sow 27 February |
| Cilantro | — | 6 February | sow 27 February |
| Corn | — | 13 April | sow 4 May |
| Cosmos | 23 March | 7 May | 28 May |
| Cucumber | 19 April | 31 May | 21 June |
| Daikon | — | 6 February | sow 27 February |
| Delphinium | 30 December | — | 27 February |
| Dill | — | 6 February | sow 27 February |
| Eggplant | 22 March | 31 May | 21 June |
| Florence fennel | 13 February | 30 March | 20 April |
| Garden sorrel | — | 6 February | sow 27 February |
| Green Beans | 7 March | 13 April | 4 May |
| Hyssop | — | — | sow 27 February |
| Kale | — | 6 February | sow 27 February |
| Kiwano | 25 March | 26 April | 17 May |
| Kohlrabi | — | 6 February | sow 27 February |
| Leek | 28 November | 6 February | 27 February |
| Lemon balm | — | 6 February | sow 27 February |
| Lettuce | — | 6 February | sow 27 February |
| Lisianthus | 11 November | 6 February | 27 February |
| Lovage | — | — | sow 27 February |
| Luffa | 19 April | 31 May | 21 June |
| Marigold | 16 February | 30 March | 20 April |
| Melon | 9 April | 31 May | 21 June |
| Microgreens | — | 7 May | sow 28 May |
| Moringa | 14 April | 8 June | 29 June |
| Mustard greens | — | 6 February | sow 27 February |
| Napa cabbage | 25 February | 30 March | 20 April |
| Nasturtium | 20 February | 30 March | 20 April |
| Okra | 19 April | 31 May | 21 June |
| Oregano | 8 December | 6 February | 27 February |
| Pansy | 12 December | 6 February | 27 February |
| Parsley | — | 6 February | sow 27 February |
| Parsnip | — | — | sow 27 February |
| Peanut | 24 April | 31 May | 21 June |
| Peas | — | 6 February | sow 27 February |
| Petunia | 29 March | 31 May | 21 June |
| Physalis | 12 March | 26 April | 17 May |
| Pumpkin | 20 March | 26 April | 17 May |
| Purple coneflower | 27 December | — | 27 February |
| Radish | — | — | sow 27 February |
| Sage | 19 December | 6 February | 27 February |
| Snapdragon | 3 December | 6 February | 27 February |
| Spinach | — | 6 February | sow 27 February |
| Stevia | 8 March | 26 April | 17 May |
| Stock | — | 6 February | sow 27 February |
| Sunflower | — | 7 May | sow 28 May |
| Sweet Corn | — | 13 April | sow 4 May |
| Sweet pea | 26 December | 6 February | 27 February |
| Sweet William | — | — | sow 27 February |
| Swiss Chard | — | 6 February | sow 27 February |
| Thyme | — | 6 February | sow 27 February |
| Tomato | 28 February | 26 April | 17 May |
| Turnip | — | 6 February | sow 27 February |
| Watercress | — | 6 February | sow 27 February |
| Watermelon | 29 April | 31 May | 21 June |
| Zinnia | 4 May | 8 June | 29 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 |
|---|---|
| Bearded Iris | 25 October |
| Crocus | 25 October |
| Daffodil | 25 October |
| Garlic | 25 October |
| Hyacinth | 25 October |
| Lily | 25 October |
| Peony | 25 October |
| Saffron | 25 October |
| Tulip | 25 October |
| Wild garlic | 25 October |
A month before the first autumn frost, so the roots grow before winter.