The climate in Portland during September can be summarized as warm and reasonably dry.
September is in the fall / autumn in Portland and is typically the 4th warmest month of the year. Daytime maximum temperatures average around 25°C (77°F), whilst at night 11°C (52°F) is normal.
| Daytime temperature | 24.7°C 76.5°F |
|---|---|
| Nightly temperature | 11.3°C 52.3°F |
| Average temperature | 18°C 64.4°F |
| Daily sunshine | 8.8 hrs |
| Avg rainfall | 75 mm 2.9 ins |
| Rainy days | 9 days |
| Sea temperature | 21.3°C 70.4°F |
| Humidity | 73% |
| Windspeed | 13.3kph 8 mph |
On average September is the 5th driest month of the year in Portland with around 75mm 2.9 inches of rain making it a reasonably dry time to visit. This rainfall is typically spread over 9 days, although this may vary considerably.
On the flip side this corresponds to an average of 8.8 hours of sunshine per day.
The data used in these monthly averages covers a period of over 100 years right up until last year. As such they are a valid prediction of what to expect for the weather in Portland in September 2025.
Best places to visit in September
| Hottest month: | July | 28.8°C 83.8°F |
|---|---|---|
| Driest month: | February | 54mm 2.1ins |
| Sunniest month: | July | 11hrs |
| Coldest month: | January | -0.3°C 31.5°F |
| Wettest month: | July | 103mm 4.1ins |