Seattle Weather in August

August's weather is some of 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 temperature, precipitation, sun, humidity, wind and storms for Seattle. The weather measurements are averages based on climate data gathered at Seattle — Tacoma International Airport, located south of the city center.

Temperature Weather iconTemperature

78 °F August average high 25 °C
57 °F August average low 14 °C

The year's highest overall temperatures that began in late July continue into August until the 8th. On these dates Seattle has daily highs averaging 79 degrees Fahrenheit (26 degrees Celsius) and lows of 58 °F (14 °C).

26 days 70 °F max. or more (21 °C)
28 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 ten days this month when the thermometer reaches into the 80s °F (over 27 °C). Temperatures of 90 °F (32 °C) or above can occur here during August.

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

Rainy Weather iconRain

1.0 in total precipitation 25 mm
5 days of rain

Half the time, Seattle receives 0.2 to 1.4 inches (6 to 34 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.


The weather data here are long-term averages provided by the US National Centers for Environmental Information (NCEI). Temperature and precipitation are 1991-2020 normals while humidity and thunderstorms are 1961-1990 normals.

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