Seattle Weather in August

August's weather is the hottest for Seattle, Washington, yet few days get really hot. The pleasant temperatures are accompanied this month by some of the sunniest and driest conditions the city sees all year.

This page gives detailed information on the typical August weather for Seattle.

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The temperature, precipitation and sunshine numbers here are historical averages based on climate data gathered at Seattle's Husky Stadium, located near downtown Seattle at the University of Washington on the shore of Lake Washington's Union Bay. The rest of the measurements are averages from the Seattle - Tacoma International Airport, located south of the city center.

Temperature Weather iconTemperature

76 °F August average high 25 °C
57 °F August average low 14 °C

In most years, Seattle averages a daily maximum temperature for August that's between 74 and 78 degrees Fahrenheit (24 to 26 degrees Celsius). The minimum temperature usually falls between 56 and 58 °F (13 to 15 °C).

August is Seattle's hottest month overall, with temperatures peaking from the 1st and 4th. These dates, along with the last two days of July, have daily highs averaging 77.2 °F (25.1 °C) and lows of 57.5 °F (14.2 °C).

26 days 70 °F max. or more (21 °C)
26 days 60 °F min. or less (16 °C)

Usually every day in August the temperature rises to over 60 °F (16 °C) at Seattle. The city averages 9 days this month when the thermometer reaches into the 80s °F (over 27 °C). Temperatures of 90 °F (32 °C) or above don't occur here every year during August.

Most August nights, the temperature drops into the 50s °F (10 to 15 °C). Yet only about twice a decade does this month get as cold as 50 °F (10 °C).

Rainy Weather iconRain

0.9 in total precipitation 24 mm
5 days of rain

Half the time, Seattle receives 0.3 to 1.1 inches (8 to 27 mm) of rainfall in August. One in four years has drier weather, while another one in four is wetter. This is the one of the least rainy months for Seattle.

Sunny Weather iconSun

56 % sunshine
10 days clear skies

The sun's rays reach the ground in Seattle during 56 percent of daylight hours on average in August, for a total of 246 hours in the month. Typically on 10 days this month the sky is mainly clear, with at most 30 percent cloud cover.

Sunlight in August at Seattle lasts for 14 hours and 11 minutes a day on average. The longest day of the month is the 1st with 14 hours and 56 minutes of daylight. By the end of the month, the days have shortened to 13:24 from sunrise to sunset. These durations can vary by a minute or two from year to year.

Humid Weather iconHumidity

68 % August average humidity

The relative humidity in Seattle during August usually peaks at 83 percent in the morning then drops to 50 percent by late afternoon.

Local Time1 am4 am7 am10 am1 pm4 pm7 pm10 pm
Humidity % 78 83 82 68 56 50 58 70

Windy Weather iconWind

7.8 mph August wind speed average 12.6 kph

August is the least windy month in Seattle.

Stormy Weather iconStorms

1 day rainfall of 0.5 inches (13 mm) or more
1 day with thunderstorms in August

Heavy rainstorms and thunderstorms don't happen every August in Seattle.


These weather data are long-term historical averages provided by the National Climatic Data Center of the United States. The temperature and precipitation numbers are 1981-2010 normals while the humidity and thunderstorm statistics are 1961-1990 normals.

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