September weather forecast and climate
Olympia, WA

The calm Capitol Lake overlooking the Washington State Capitol building in Olympia, Washington
The calm Capitol Lake overlooking the Washington State Capitol building in Olympia, Washington
September, the first month of the autumn, in Olympia, is also an agreeable month, with temperature in the range of an average low of 47.7°F (8.7°C) and an average high of 70.5°F (21.4°C).

Temperature

In September, the average high-temperature marginally drops, from a warm 78.6°F (25.9°C) in August, to an agreeable 70.5°F (21.4°C). The average low-temperature, in Olympia, is 47.7°F (8.7°C).

Humidity

The average relative humidity in September is 78%.

Rainfall

In Olympia, Washington, in September, it is raining for 11.7 days, with typically 1.81" (46mm) of accumulated precipitation. Throughout the year, there are 177.4 rainfall days, and 37.05" (941mm) of precipitation is accumulated.

Snowfall

In Olympia snow does not fall in April through October.

Daylight

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

Sunshine

In Olympia, the average sunshine is 8.3h.

UV index

The average daily maximum UV index in September is 4. A UV Index value of 3 to 5 symbolizes a moderate threat to health from the exposure to the Sun's UV rays for the average person.
Note: In September, the average maximum UV index of 4 translate into the following recommendations:
Take precautions - Protection against sunburn is recommended. The solar radiation is most powerful near the mid-day, so the exposure to the direct Sun should be reduced accordingly. On bright days sunglasses that block both UVA and UVB rays should be worn. A hat with a wide brim is extremely helpful, as it can prevent roughly 50% of UV radiation from reaching the eyes.

What is the temperature in September in Olympia?

The average high-temperature, in September, in Olympia, is 70.5°F (21.4°C), while the average low-temperature is 47.7°F (8.7°C).

What is the average humidity in September in Olympia?

The average relative humidity in September in Olympia is 78%.

How much does it rain in Olympia in September?

In Olympia, Washington, in September, it is raining for 11.7 days, with typically 1.81" (46mm) of accumulated precipitation.

When it does not snow in Olympia?

April through October are months without snowfall in Olympia.

What is the average length of the day in September in Olympia?

The average length of the day in September in Olympia is 12.5h.

How many hours of sunshine does Olympia have in September?

The average sunshine in September is 8.3h.

What is the UV index reading in September in Olympia?

In September, the average daily maximum UV index is 4. A UV Index reading of 3 to 5 represents a moderate health threat from unprotected exposure to the UV radiation.
Average temperature in September - Olympia, WA
  • Average high temperature in September: 21.4°C

The warmest month (with the highest average high temperature) is August (25.9°C).
The month with the lowest average high temperature is December (6.1°C).

  • Average low temperature in September: 8.7°C

The month with the highest average low temperature is August (10.3°C).
The coldest month (with the lowest average low temperature) is December (0.8°C).

Average pressure in September - Olympia, WA
  • Average pressure in September: 1016.5mbar

The month with the highest atmospheric pressure is January (1018.9mbar).
The month with the lowest atmospheric pressure is March (1016.4mbar).

Average wind speed in September - Olympia, WA
  • Average wind speed in September: 6.1km/h

The windiest months (with the highest average wind speed) are March and November (7.4km/h).
The calmest month (with the lowest average wind speed) is September (6.1km/h).

Average humidity in September - Olympia, WA
  • Average humidity in September: 78%

Months with the highest relative humidity are January, November and December (89%).
The month with the lowest relative humidity is July (71%).

Average rainfall in September - Olympia, WA
  • Average rainfall in September: 46mm

The wettest month (with the highest rainfall) is December (147mm).
The driest month (with the least rainfall) is July (10mm).

Average rainfall days in September - Olympia, WA
  • Average rainfall days in September: 11.7 days

The month with the highest number of rainy days is March (20.4 days).
The month with the least rainy days is August (5.5 days).

Average snowfall in September - Olympia, WA
  • Average snowfall in September: 0mm

The month with the highest snowfall is February (59mm).
Months with the least snowfall are April, May, June, July, August, September and October (0mm).

Average snowfall days in September - Olympia, WA
  • Average snowfall days in September: 0 days

The month with the highest number of snowfall days is February (3.3 days).
Months with the least snowfall days are May, June, July, August, September and October (0 days).

Average daylight in September / Average sunshine in September - Olympia, WA
  • Average daylight in September: 12.5h

The month with the longest days is June (Average daylight: 15.8h).
The month with the shortest days is December (Average daylight: 8.6h).

  • Average sunshine in September: 8.3h

The month with the most sunshine is August (Average sunshine: 10.2h).
The month with the least sunshine is December (Average sunshine: 3.4h).

Average sunshine days in September - Olympia, WA
  • Average sunshine days in September: 16.1 days

The month with the most sunshine days is August (22.4 days).
The month with the least sunshine days is February (8.4 days).

Average UV index in September - Olympia, WA
  • Average UV index in September: 4

Months with the highest UV index are June and July (UV index 5).
Months with the lowest UV index are January, February, November and December (UV index 2).

Average cloud cover in September - Olympia, WA
  • Average cloud cover in September: 45

Months with the most cloud cover are January and December (Cloud cover 65).
Months with the least cloud cover are July and August (Cloud cover 35).

Average visibility in September - Olympia, WA
  • Average visibility in September: 7km

Months with the highest visibility are June, July and August (8km).
Months with the lowest visibility are January, February, November and December (6km).