Frost dates in Seattle: last spring frost and first autumn frost
When is it safe to plant out in Seattle, and when does the first frost come? Dates from 45 years of nightly minimum temperatures (1981–2025), with how early or late they can fall.
Frost dates in Seattle and how sure they are
| Early year (1 in 10) | Typical (median) | Late year (1 in 10) | |
|---|---|---|---|
| Last spring frost | 21 February | 9 March | 8 April |
| First autumn frost | 29 October | 19 November | 10 December |
In a typical year the last frost in Seattle falls around 9 March and the first one around 19 November, leaving about 247 frost-free days (between 222 and 287 in 8 years out of 10). To be safe, plant tender crops after 8 April: by then the last frost has passed in 9 years out of 10. Bring them in before 29 October: in 1 year in 10 the first frost comes earlier.
Frost month by month in Seattle
| Month | Average low | Coldest night (avg) | Record low | Frost nights | Years with frost |
|---|---|---|---|---|---|
| January | 1.8 °C | -4.2 °C | -12.6 °C | 8.2 | 96% |
| February | 1.8 °C | -3.9 °C | -16.1 °C | 7.2 | 87% |
| March | 3.4 °C | -1.1 °C | -5.7 °C | 2.6 | 82% |
| April | 5 °C | 1.1 °C | -1.7 °C | 0.2 | 11% |
| May | 8.1 °C | 3.8 °C | -0.2 °C | 0 | 2% |
| June | 10.5 °C | 6.9 °C | 4.5 °C | 0 | 0% |
| July | 12.9 °C | 9.7 °C | 6.1 °C | 0 | 0% |
| August | 13.3 °C | 10 °C | 7.5 °C | 0 | 0% |
| September | 11 °C | 7.1 °C | 3.9 °C | 0 | 0% |
| October | 7.3 °C | 2.2 °C | -3.4 °C | 0.4 | 24% |
| November | 3.9 °C | -1.8 °C | -14.5 °C | 3.5 | 76% |
| December | 1.5 °C | -4.4 °C | -14.8 °C | 8.6 | 96% |
Frost here means a night minimum at or below 0 °C at 2 m. Frost nights is the average count per month; years with frost is how many years had at least one.
Frost alerts for your garden or field
LayEarth Business Agro sends an alert when the forecast low at your saved site drops below your threshold (0 °C by default), with frost risk, hours below zero and white or black frost for each forecast day. LayEarth Pro, from 9 USD a month, adds alerts for the places you follow.
Temperature map around Seattle
The live temperature layer of the map (NOAA GFS forecast): watch the cold nights coming hour by hour.
More for Seattle
Weather in Seattle now · Will it rain today in Seattle? · Open the temperature map on Seattle
Questions
- When is the last frost in Seattle?
- On average around 9 March. In an early year the last frost comes by 21 February, in a late one (1 year in 10) after 8 April.
- When is the first frost in Seattle?
- On average around 19 November. In 1 year in 10 it comes before 29 October, in a mild year not until 10 December.
- How long is the growing season in Seattle?
- About 247 frost-free days between the last spring frost and the first autumn frost, from 222 in a short year to 287 in a long one.
- When can I plant tomatoes in Seattle?
- Frost-tender plants such as tomatoes, peppers, beans and courgettes go out after the last frost: after 8 April the risk is down to 1 year in 10. Hardy crops can go earlier.
- How cold does it get in Seattle?
- The coldest night of winter averages -7.2 °C; the lowest since 1981 was -16.1 °C in 1989.
Frost dates nearby
Vancouver · Portland · Calgary · Edmonton · Salt Lake City · Las Vegas
How these dates are computed
Daily minimum temperature at 2 m from NASA POWER (MERRA-2 reanalysis, public domain), 1981–2025, corrected from the ~50 km grid to the real altitude of Seattle (6.5 °C per km). For each year: the last night at or below 0 °C before midsummer and the first one after it; the dates are the median and the 10% / 90% of those years. A garden in a frost pocket or a city centre can differ by days. Live temperatures: the temperature layer of the map.