Seattle in December: what to plant
Over the last 5 years, December in Seattle has run 3.8–8.1°C with about 201 mm of rain across the month. Here is what weather like that will carry to harvest.
Everything above is a five-year average. In the game it is this — the weather Seattle is actually having, today.
Grow one in Seattle's weather right now →❄️ In 4 of the last 5 years, Seattle saw at least one night at or below 0°C in December (record low -6.5°C). Cold-sensitive crops need cover.
🗓️ This month still falls inside the frost season. Average last spring frost around Mar 1, first autumn frost around Dec 9 — roughly 283 frost-free days. Sow tender crops after the last frost date and make sure they finish before the first.
☀️ About 3.3 h of sunshine a day this month. Within the month it cools by about 1.4°C from the first ten days to the last — the window for autumn sowings is opening.
Sow this month — when would you harvest?
Assuming you sow in mid-December, then adding up the warmth Seattle usually gets, one day at a time — which is why some of these run past the end of the month.
| Crop | Days | Harvest around |
|---|---|---|
| 🌱 Microgreens | 8 | Dec 22 |
| 🌿 Spinach | 139 | May 2 |
| 🌿 Rocket | 134 | Apr 27 |
| 🧄 Garlic | 154 | May 17 |
| 🍃 Mint | 30 | Jan 13 |
| 🧅 Chives | 32 | Jan 15 |
| 🌿 Basil | 34 | Jan 17 |
🌡️ Tomato, Chili Pepper, Yardlong bean, Bitter melon, Luffa, Winter melon, Aubergine, Okra never accumulate enough heat outdoors in Seattle — not in any month. Locally these need a greenhouse or a warm windowsill.
Best crops to sow now
- 🌱 Microgreens Ideal about 8 days to harvest 🪴 Windowsill pot — sheltered from outdoor weather
- 🌿 Spinach Marginal about 188 days to harvest Recent mean 5.9°C — right in the sweet spot
- 🌿 Rocket Marginal about 191 days to harvest Recent mean 5.9°C is too cold (ideal 6–22°C)
- 🧄 Garlic Marginal about 203 days to harvest Recent mean 5.9°C — right in the sweet spot
- 🍃 Mint Ideal about 30 days to harvest 🪴 Windowsill pot — sheltered from outdoor weather
- 🧅 Chives Ideal about 32 days to harvest 🪴 Windowsill pot — sheltered from outdoor weather
- 🌿 Basil Ideal about 34 days to harvest 🪴 Windowsill pot — sheltered from outdoor weather
Leave these for another month
- 🌶️ Okra — Recent mean 5.9°C is too cold (ideal 20–33°C)
- 🍆 Aubergine — Recent mean 5.9°C is too cold (ideal 18–32°C)
- 🍈 Winter melon — Recent mean 5.9°C is too cold (ideal 18–32°C)
Other months in Seattle
📍 Somewhere else? Look up your own city →
Temperature and rainfall come from Open-Meteo's historical observations for Seattle, averaged day by day over the last 5 years. Whether a crop finishes in time is worked out from its own starting temperature and heat requirement — those numbers are listed on each crop page if you want to check them.