Portland weather in September
September in Portland: warm, a little rain, with clean air — an excellent time to visit.
#3 of 12 months in Portland · #73 of 604 destinations to visit in September · comfort 90/100 (tier S)
Updated June 2026 · climate normals from ERA5 reanalysis
Portland climate normals — September
| Daytime high | 26°C / 78°F | 🌤 warm |
|---|---|---|
| Nighttime low | 14°C / 56°F | |
| Feels like (high) | 25°C / 77°F | |
| Rainfall | 58 mm / 2.3 in | 🌦 some rain |
| Rainy days | 7 days | |
| Humidity | 63% | 💧 humid |
| Dew point | 10°C / 51°F | |
| Sunshine | 9.6 h/day | |
| Daylight | 12.5 h | |
| Wind | 12 km/h / 7 mph | |
| Air quality (US AQI) | 33 | 🍃 good |
Monthly averages from ERA5 reanalysis. AQI is the mean US Air Quality Index for the month.
Where is Portland?
Loading map…
Portland in September — FAQ
- Is September a good time to visit Portland?
- September in Portland: warm, a little rain, with clean air — an excellent time to visit. It ranks #3 of 12 months for Portland on SeasonMap's comfort score (90/100).
- What is the weather like in Portland in September?
- In September, Portland averages a daily high of 25.7°C and a low of 13.5°C, with about 58.4 mm of rain over roughly 7 rainy days.
- What is the air quality in Portland in September?
- Portland has a mean US Air Quality Index of about 33 in September.