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The tables below display average monthly climate and weather indicators in Seattle Sea-tac Airport Washington.
Seattle Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual
Avg. Temperature 4.5 6.4 7.6 9.6 12.8 16.1 18.4 18.6 15.9 11.6 7.4 4.7 11.1
Avg. Max Temperature 7.2 9.7 11.5 14.0 17.7 21.1 24.0 24.0 20.7 15.4 10.3 7.3 15.2
Avg. Min Temperature 1.8 3.0 3.6 5.1 7.9 11.1 12.9 13.2 11.1 7.7 4.5 2.1 7.0
Days with Max Temp of 32 C or Higher 0.0 0.0 0.0 0.0 < 0.5 < 0.5 1.0 1.0 < 0.5 0.0 0.0 0.0 2.0
Days with Min Temp Below Freezing 10.0 6.0 3.0 < 0.5 0.0 0.0 0.0 0.0 0.0 < 0.5 3.0 9.0 30.0
   
Seattle Sea-tac Airport Heating and Cooling Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual
Heating Degree Days 772 602 601 474 307 144 58.0 65.0 156 378 591 760 4908
Cooling Degree Days 0.0 0.0 0.0 0.0 0.0 21.0 64.0 81.0 24.0 0.0 0.0 0.0 190
   
Seattle Sea-tac Airport Precipitation Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual
Precipitation (inches) 5.4 4.0 3.5 2.3 1.7 1.5 0.8 1.1 1.9 3.2 5.8 5.9 37.2
Days with Precipitation 0.01 inch or More 19.0 16.0 17.0 14.0 10.0 9.0 5.0 6.0 9.0 13.0 18.0 19.0 155
Monthly Snowfall (inches) 4.9 1.6 1.3 0.1 < 0.05 0.0 < 0.05 0.0 < 0.05 0.0 1.1 2.4 11.4
   
Other Seattle Sea-tac Airport Weather Indicators Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual
Average Wind Speed 9.6 9.5 9.5 9.4 8.9 8.7 8.2 7.8 8.1 8.5 9.3 9.6 8.9
Clear Days 3.0 3.0 3.0 3.0 4.0 5.0 10.0 9.0 8.0 4.0 2.0 2.0 58.0
Partly Cloudy Days 4.0 4.0 6.0 7.0 9.0 8.0 10.0 10.0 9.0 7.0 4.0 4.0 82.0
Cloudy Days 24.0 21.0 22.0 20.0 18.0 17.0 11.0 12.0 13.0 19.0 23.0 25.0 226
Percent of Possible Sunshine 28.0 40.0 50.0 52.0 56.0 56.0 65.0 65.0 62.0 43.0 28.0 23.0 47.0
Avg. Relative Humidity 60.0 77.0 75.0 72.5 70.5 69.0 67.0 66.0 68.0 72.0 75.5 78.5 80.5