August weather forecast
Seattle, WA

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Beautiful dusk skyline over the giant skyscrapers of Seattle, Washington
Beautiful dusk skyline over the giant skyscrapers of Seattle, Washington

Weather in August

August maintains the summer heat, with temperatures nearly mirroring July's highs. Rain becomes even more scarce, and the city revels in clear, sun-drenched days. As the warmest sea temperatures take hold, August asserts itself as an excellent time for swim enthusiasts to take a dip in the calm waters. Its quintessential summer weather coincides with an array of outdoor events and festivals, contributing to the joyful atmosphere all around the city. Summer in Seattle is at its peak and the city is alive with energy and excitement.

Temperature

In Seattle, the peak temperatures are generally noted in August, averaging a high of 76.3°F (24.6°C) and a low of 54°F (12.2°C).

Humidity

In Seattle, the average relative humidity in August is 70%.

Rainfall

July and August are months with the least rain when the rain falls for 2.8 days and typically aggregates up to 0.12" (3mm) of rain.

Snowfall

April through October and December are months without snowfall.

Ocean temperature

With an average ocean temperature of 53.6°F (12°C), August is the month with the warmest seawater.
Note: It is life-risking to swim in 53.6°F (12°C). Briefly staying in 55.4°F (13°C) waters feels unsettling, and temperatures below 50°F (10°C) might result in cold shock and loss of breath control, hinging on personal endurance.

Daylight

In Seattle, Washington, the average length of the day in August is 14h and 12min.
On the first day of the month, sunrise is at 5:48 am and sunset at 8:43 pm. On the last day of August, sunrise is at 6:27 am and sunset at 7:50 pm PDT.

Sunshine

With an average of 10.7h of sunshine, August has the most sunshine of the year in Seattle, Washington.

UV index

In August, the average daily maximum UV index in Seattle is 4. A UV Index reading of 3 to 5 represents a moderate health risk from unsafe exposure to UV radiation for the average person.
Note: A maximum UV index of 4 in August translates into the following recommendations:
Heed the precautions - Protecting the skin and eyes from damage is compulsory. Midday is the peak time for the Sun's radiation; stay in the shade and protect yourself. Shield yourself from the harmful effects of UV radiation with sun-protective attire, a hat, and quality sunglasses.
Resources | Updated: Feb 14, 2024 | Published by: Weather U.S.

Frequently asked questions

What month is the hottest in Seattle?

Seattle's August weather reaches an average high of 76.3°F (24.6°C) and an average low of 54°F (12.2°C), making it the warmest month.

What are the temperatures in Seattle in August?

The high-temperature, in August, in Seattle, is 76.3°F (24.6°C), while the low-temperature averages to 54°F (12.2°C).

What is the average humidity in August in Seattle?

In August, the average relative humidity in Seattle is 70%.

What is the driest month in Seattle?

July and August are months with the least rain when the rain falls for 2.8 days and typically aggregates up to 0.12" (3mm) of rain.

How much does it rain in Seattle in August?

In Seattle, in August, it is raining for 2.8 days, with typically 0.12" (3mm) of accumulated precipitation.

When it does not snow in Seattle?

April through October and December are months without snowfall.

What is the month with the warmest ocean in Seattle?

With an average ocean temperature of 53.6°F (12°C), August is the month with the warmest seawater.

What is the water temperature in August in Seattle?

In August, the average ocean temperature in Seattle, Washington, is 53.6°F (12°C). Swimming in 53.6°F (12°C) is considered dangerous. Unprotected immersion in temperatures below 50°F (10°C) causes quickly maximum intensity cold shock with hyperventilation.

What is the average length of the day in August in Seattle?

In Seattle, the average day length in August is 14h and 12min.

When are sunrise and sunset in August in Seattle?

In August, on the first day of the month, sunrise is at 5:48 am and sunset at 8:43 pm. On the last day of the month, in Seattle, Washington, sunrise is at 6:27 am and sunset at 7:50 pm PDT.

What month has the most sunshine in Seattle?

With an average of 10.7h of sunshine, August has the most sunshine of the year in Seattle, Washington.

How many hours of sunshine does Seattle have in August?

The average sunshine duration in August in Seattle is 10.7h.

What is the UV index reading in August in Seattle?

The average daily maximum UV index in August in Seattle, Washington, is 4. A UV Index of 3 to 5 symbolizes a medium hazard to health from unprotected exposure to UV radiation.
Average humidity
Average rainfall days
Average snowfall
Average snowfall days
Average daylight
Average sunshine
Average sunshine days
Average UV index
Average cloud cover
Average visibility

Average temperature in August
Seattle, WA

Average temperature in August - Seattle, WA
  • Average high temperature in August: 76.3°F

The warmest month (with the highest average high temperature) is August (76.3°F).
The month with the lowest average high temperature is December (43.7°F).

  • Average low temperature in August: 54°F

The month with the highest average low temperature is August (54°F).
The coldest month (with the lowest average low temperature) is December (35.1°F).

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Average pressure in August
Seattle, WA

Average pressure in August - Seattle, WA
  • Average pressure in August: 30.01"Hg

The month with the highest atmospheric pressure is January (30.1"Hg).
The months with the lowest atmospheric pressure are March, August and September (30.01"Hg).

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Average wind speed in August
Seattle, WA

Average wind speed in August - Seattle, WA
  • Average wind speed in August: 3.5mph

The windiest month (with the highest average wind speed) is March (5.3mph).
The calmest months (with the lowest average wind speed) are July and August (3.5mph).

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Average humidity in August
Seattle, WA

Average humidity in August - Seattle, WA
  • Average humidity in August: 70%

The month with the highest relative humidity is January (85%).
The month with the lowest relative humidity is July (69%).

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Average rainfall in August
Seattle, WA

Average rainfall in August - Seattle, WA
  • Average rainfall in August: 0.12"

The wettest month (with the highest rainfall) is December (0.87").
The driest months (with the least rainfall) are July and August (0.12").

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Average rainfall days in August
Seattle, WA

Average rainfall days in August - Seattle, WA
  • Average rainfall days in August: 2.8 days

The month with the highest number of rainy days is November (9.1 days).
The month with the least rainy days is August (2.8 days).

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Average snowfall in August
Seattle, WA

Average snowfall in August - Seattle, WA
  • Average snowfall in August: 0"

The month with the highest snowfall is February (0.71").
The months with the least snowfall are April, May, June, July, August, September, October and December (0").

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Average snowfall days in August
Seattle, WA

Average snowfall days in August - Seattle, WA
  • Average snowfall days in August: 0 days

The month with the highest number of snowfall days is February (1.9 days).
The months with the least snowfall days are May, June, July, August, September and October (0 days).

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Average sea temperature in August
Seattle, WA

Average sea temperature in August - Seattle, WA
  • Average sea temperature in August: 53.5°F

The best month for swimming (with the highest average sea temperature) is August (53.5°F).
The coldest month (with the lowest average sea temperature) is February (45.3°F).

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Average daylight in August /
Average sunshine in August
Seattle, WA

Average daylight in August / Average sunshine in August - Seattle, WA
  • Average daylight in August: 14h and 1min

The month with the longest days is June (Average daylight: 15h and 54min).
The month with the shortest days is December (Average daylight: 8h and 30min).

  • Average sunshine in August: 10h and 4min

The month with the most sunshine is August (Average sunshine: 10h and 42min).
The month with the least sunshine is December (Average sunshine: 4h and 18min).

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Average sunshine days in August
Seattle, WA

Average sunshine days in August - Seattle, WA
  • Average sunshine days in August: 25.9 days

The month with the most sunshine days is August (25.9 days).
The month with the least sunshine days is November (16.8 days).

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Average UV index in August
Seattle, WA

Average UV index in August - Seattle, WA
  • Average UV index in August: 4

The month with the highest UV index is July (UV index 6).
The months with the lowest UV index are January, February, November and December (UV index 2).

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Average cloud cover in August
Seattle, WA

Average cloud cover in August - Seattle, WA
  • Average cloud cover in August: 25

The month with the most cloud cover is December (Cloud cover 56).
The month with the least cloud cover is August (Cloud cover 25).

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Average visibility in August
Seattle, WA

Average visibility in August - Seattle, WA
  • Average visibility in August: 6mi

The months with the highest visibility are April, May, June, July, August, September and October (6mi).
The months with the lowest visibility are January, February, March, November and December (5mi).

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Seattle, Washington, USA

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