Portland Weather in September

The climate in Portland during September can be summarized as mild and a little damp.

September is in the fall / autumn in Portland and is typically the 4th warmest month of the year. Daytime maximum temperatures average around 21°C (70°F), whilst at night 10°C (50°F) is normal.

On average September is the 3rd driest month of the year in Portland with around 81mm 3.2 inches of rain making it a a little damp 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 8.1 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.