Frost dates in Portland: last spring frost and first autumn frost
When is it safe to plant out in Portland, 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 Portland and how sure they are
| Early year (1 in 10) | Typical (median) | Late year (1 in 10) | |
|---|---|---|---|
| Last spring frost | 16 February | 13 March | 13 April |
| First autumn frost | 29 October | 21 November | 6 December |
In a typical year the last frost in Portland falls around 13 March and the first one around 21 November, leaving about 250 frost-free days (between 216 and 282 in 8 years out of 10). To be safe, plant tender crops after 13 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 Portland
| Month | Average low | Coldest night (avg) | Record low | Frost nights | Years with frost |
|---|---|---|---|---|---|
| January | 2.2 °C | -4.7 °C | -14.5 °C | 8 | 93% |
| February | 2.3 °C | -4.1 °C | -17.6 °C | 6 | 91% |
| March | 3.9 °C | -0.8 °C | -6.8 °C | 2.2 | 73% |
| April | 5.4 °C | 1.2 °C | -1.2 °C | 0.2 | 16% |
| May | 8.3 °C | 3.9 °C | 0.8 °C | 0 | 0% |
| June | 10.7 °C | 7.1 °C | 4.4 °C | 0 | 0% |
| July | 13.1 °C | 9.6 °C | 6.3 °C | 0 | 0% |
| August | 13.9 °C | 10.3 °C | 8 °C | 0 | 0% |
| September | 11.7 °C | 7.4 °C | 2.9 °C | 0 | 0% |
| October | 7.9 °C | 2 °C | -3.2 °C | 0.4 | 20% |
| November | 4.4 °C | -1.8 °C | -15 °C | 3.5 | 71% |
| December | 1.8 °C | -4.9 °C | -16.9 °C | 9.1 | 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 Portland
The live temperature layer of the map (NOAA GFS forecast): watch the cold nights coming hour by hour.
More for Portland
Will it rain today in Portland? · Open the temperature map on Portland
Questions
- When is the last frost in Portland?
- On average around 13 March. In an early year the last frost comes by 16 February, in a late one (1 year in 10) after 13 April.
- When is the first frost in Portland?
- On average around 21 November. In 1 year in 10 it comes before 29 October, in a mild year not until 6 December.
- How long is the growing season in Portland?
- About 250 frost-free days between the last spring frost and the first autumn frost, from 216 in a short year to 282 in a long one.
- When can I plant tomatoes in Portland?
- Frost-tender plants such as tomatoes, peppers, beans and courgettes go out after the last frost: after 13 April the risk is down to 1 year in 10. Hardy crops can go earlier.
- How cold does it get in Portland?
- The coldest night of winter averages -8.1 °C; the lowest since 1981 was -17.6 °C in 1989.
Frost dates nearby
Seattle · Vancouver · Calgary · Salt Lake City · Edmonton · 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 Portland (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.