Portland
Oregon, USA
Long-term weather forecast
Long-term weather forecast

September weather forecast and climate
Portland, OR

A colorful autumn view of the outline of Portland City, Oregon, with mountains in the distance
A colorful autumn view of the outline of Portland City, Oregon, with mountains in the distance
September brings pleasant weather to Portland as the autumn begins to ascend over the city's landscape. The average temperatures are in the warm zone of 53.1°F (11.7°C) to 75.9°F (24.4°C) with light rainfall to the tune of 1.5" (38.1mm).
The skies are mostly clear, with 8 hours of bright sunshine and 13-hour days. The fall season starts in earnest by the third week of September when the leaves start to change color rapidly. Evenings are breezy with plenty of daylight for a walk around the historic lanes and beautiful trails. Occasionally, a cold front may spring a surprise during the early fall season.

What is the temperature in September in Portland?

The average high-temperature, in September, is 75.7°F (24.3°C), while the average low-temperature is 53.1°F (11.7°C).

What is the average humidity in September in Portland?

In Portland, Oregon, the average relative humidity in September is 69.4%.

How many days does it rain in September in Portland?

In Portland, in September, during 6.7 rainfall days, 1.5" (37.3mm) of precipitation is typically accumulated.

When it does not snow in Portland?

In Portland, Oregon, snow does not fall in April through October.

How many hours of daylight does Portland have in September?

In September, the average length of the day in Portland is 12.5h.

How many hours of sunshine does Portland have in September?

In Portland, the average sunshine in September is 7.9h.

What is the UV index intensity in September in Portland?

The average daily maximum UV index in September in Portland is 5. A UV Index of 3 to 5 symbolizes a moderate vulnerability from the exposure to the Sun's UV radiation.
Average temperature in September - Portland, OR
  • Average high temperature in September: 75.8°F

The warmest month (with the highest average high temperature) is August (81.1°F).
The month with the lowest average high temperature is December (45.6°F).

  • Average low temperature in September: 53.1°F

The month with the highest average low temperature is August (58°F).
The coldest month (with the lowest average low temperature) is December (35.2°F).

Average humidity in September - Portland, OR
  • Average humidity in September: 69.4%

The month with the highest relative humidity is December (82.7%).
The month with the lowest relative humidity is July (62.8%).

Average rainfall in September - Portland, OR
  • Average rainfall in September: 1.5"

The wettest month (with the highest rainfall) is November (5.6").
Driest months (with the lowest rainfall) are July and August (0.7").

Average rainfall days in September - Portland, OR
  • Average rainfall days in September: 6.7 days

The month with the highest number of rainy days is November (19 days).
The month with the lowest number of rainy days is August (3.9 days).

Average snowfall in September - Portland, OR
  • Average snowfall in September: 0"

The month with the highest snowfall is February (2.1").
Months with the lowest snowfall are April, May, June, July, August, September and October (0").

Average snowfall days in September - Portland, OR
  • Average snowfall days in September: 0 days

Months with the highest number of snowfall days are February and December (1.5 days).
Months with the lowest number of snowfall days are April, May, June, July, August, September and October (0 days).

Average daylight in September / Average sunshine in September - Portland, OR
  • Average daylight in September: 12.5h

The month with the longest days is June (Average daylight: 15.6h).
The month with shortest days is December (Average daylight: 8.8h).

  • Average sunshine in September: 7.9h

The month with most sunshine is July (Average sunshine: 10.7h).
The month with least sunshine is December (Average sunshine: 2.1h).

Average UV index in September - Portland, OR
  • Average UV index in September: 5

The month with the highest UV index is July (UV index 8).
Months with the lowest UV index are January and December (UV index 1).