Climate averages 1991–2020
Portland weather
in September.
A warm, moderately wet month: the 3rd warmest and the 3rd driest of the year. Meets the pleasant-weather rule
Long-term climate patterns, not a forecast for a particular trip.
September is a warm month in Portland: daytime highs average 24.1°C and nights cool to about 12.3°C. By daytime temperature it is the 3rd warmest of the 12 months.
Expect about 42 mm of rain on roughly 6 days, which makes September a moderately wet month (the 3rd driest of the 12 months). Daylight, from sunrise to sunset, lasts about 12 h 35 min on an average September day.
The nearest other city in this atlas is Beaverton (11 km away). In September its highs average 23.7°C, about as warm as Portland, with 42 mm of rain.
Among the 498 cities listed in the United States, Portland ranks joint 350th of 498 for the warmest September highs and joint 166th of 498 for the driest September (rainfall, lowest first). The mean September high of those 498 cities is 26.9°C; Portland is 2.8°C cooler than that mean.
From September to October, average highs fall by 7.1°C to 17.0°C, and monthly rainfall rises from 42 mm to 106 mm.
The annual picture
September in context
Monthly rainfall
Average total · mmAverages from hourly ERA5 reanalysis data. Actual weather varies from year to year. How these numbers are calculated
Every month, side by side
Portland climate table
| Month | Average highHigh / low | Average low | Rainfall mm/month | Rain days ≥1 mm/day | Daylight hours/dayDaylight h/day |
|---|---|---|---|---|---|
| January | 8.4°C1.7°C | 1.7°C | 167 | 17.3 | 9.19 h |
| February | 10.1°C2.0°C | 2.0°C | 130 | 15.0 | 10.310 h |
| March | 12.4°C3.4°C | 3.4°C | 145 | 17.5 | 11.912 h |
| April | 14.9°C5.4°C | 5.4°C | 115 | 16.1 | 13.513 h |
| May | 18.8°C8.8°C | 8.8°C | 70 | 11.1 | 14.915 h |
| June | 21.8°C11.3°C | 11.3°C | 43 | 7.6 | 15.616 h |
| July | 27.1°C14.1°C | 14.1°C | 12 | 2.3 | 15.315 h |
| August | 27.6°C14.6°C | 14.6°C | 14 | 2.6 | 14.114 h |
| September, selected | 24.1°C12.3°C | 12.3°C | 42 | 6.2 | 12.613 h |
| October | 17.0°C8.1°C | 8.1°C | 106 | 11.8 | 11.011 h |
| November | 11.1°C4.2°C | 4.2°C | 174 | 17.3 | 9.610 h |
| December | 7.7°C1.7°C | 1.7°C | 193 | 18.0 | 8.89 h |
Rainfall is the average of the 30 separate monthly totals. A rain day is a local calendar day with at least 1 mm of precipitation. Daylight is the calculated sunrise-to-sunset length, not measured sunshine.
Compare places
September in nearby cities
- Beaverton in SeptemberUnited States · 11 kmHigh 23.7°C · Low 12.0°C · 42 mm rain
- Vancouver, United States in SeptemberUnited States · 13 kmHigh 23.5°C · Low 12.0°C · 62 mm rain
- Gresham in SeptemberUnited States · 19 kmHigh 22.8°C · Low 11.3°C · 58 mm rain
- Hillsboro in SeptemberUnited States · 24 kmHigh 23.7°C · Low 12.2°C · 43 mm rain
- Salem, United States in SeptemberUnited States · 70 kmHigh 24.5°C · Low 12.0°C · 32 mm rain
- Eugene in SeptemberUnited States · 167 kmHigh 24.3°C · Low 11.3°C · 41 mm rain
- Tacoma in SeptemberUnited States · 193 kmHigh 20.8°C · Low 11.9°C · 50 mm rain
- Bend in SeptemberUnited States · 195 kmHigh 22.9°C · Low 7.9°C · 16 mm rain
Read the numbers correctly
Climate, not a promise.
These patterns help compare months. They cannot tell you the weather on a specific day of your trip.
Sources, method and limitsHow these numbers are made (what the highs, lows and rain days mean, the sources and the model cell used for Portland) is explained once on the Portland year overview and on the Sources, method and limits page.
Beaverton lies in the same rainfall cell, so its rainfall figures are identical to these; temperatures differ because they come from smaller 0.1° cells.