Weather in Portland in September 2025
Average weather
Average temperature in Portland in September
The temperature in September is +75°F on average, with a range between a maximum of +91°F during the day and a minimum of +48°F at night.
The average maximum temperature goes down 33% by the end of the month, compared with the beginning of the month, from +81°F to +66°F.
Is Portland warm or cold in September?
Portland is typically warm in September.
Maximum temperatures go down compared to the previous month from +82°F to +77°F. The minimum temperature also goes down from +57°F to +54°F.
It’s generally warm, but pack a long-sleeve shirt for evenings.
September is one of the warmest months in Portland, here is the comparison with other months:
Climate in Portland in September
| August | September | October | ||||
|---|---|---|---|---|---|---|
| Avg. temperature | ||||||
| +82°F | +77°F | +64°F | ||||
| Min. temperature | ||||||
| +45°F | +37°F | +28°F | ||||
| Max. temperature | ||||||
| +106°F | +106°F | +90°F | ||||
| Rainfall | ||||||
| 16 mm | 49 mm | 105 mm | ||||
| Wind | ||||||
| 1 m/s | 1 m/s | 1 m/s | ||||
| Humidity | ||||||
| 63% | 68% | 78% | ||||
| Air pressure | ||||||
| 1015 HPa | 1015 HPa | 1017 HPa | ||||
| Sunny days | ||||||
| 12 | 10 | 5 | ||||
| Cloudy days | ||||||
| 12 | 10 | 9 | ||||
| Rainy days | ||||||
| 6 | 10 | 16 | ||||
| Snowy days | ||||||
| 0 | 0 | 0 | ||||
September typically has worse weather conditions compared to August. It’s getting colder in September. From +82°F in the day, the average maximum temperature lowers to +77°F. Prepare for more rain. Average rainfall goes from 16 mm to 49 mm. Humidity rises from 63% to 68%. The average wind speed doesn’t change much during September, staying around 1 m/s. The days becoming less sunny, going from 12 sunny days in August to 10 in September.
Next month (October) brings a further decline in the weather.
Wind
The average wind speed is 2 m/s getting up to 5 m/s which is a light breeze; barely moving the tree leaves.
The average wind speed in Portland is gradually increasing during September, going from 2 m/s to 2 m/s over the course of the month.
Rain
How was the weather last September in Portland?
Climate Change Over the Years
The climate in Portland in September has not changed that much over the last 43 years.
The average temperature was the lowest in 2011 (+61°F) and the highest in 2015 (+67°F). The driest year was 1985 with only 736 mm of rainfall, and the wettest year was 2021 with 4296 mm.
FAQ
Is September a good time to visit Portland?
Can you sunbathe in Portland in September?
Is Portland rainy in September?
Is it sunny in Portland in September?
Other cities in USA
Monthly weather in Portland
Source of the data
For this page, we’ve looked at the typical weather in Portland, based on historical hourly weather data from January 1, 1979, to December 31, 2023.
For past dates, we show actual recorded data at the location at that time. Forecasts are based on recorded weather during that day of the year, averaged over the total years for which we have records (unless stated otherwise). The daily temperature is the highest recorded temperature in the shadow during that day.