Weather and Climate

 

Weather and climate change; words seemingly in the news almost each day. Ask anyone what Seattle's weather is like and you'll hear words like rainy, cool, wet, stormy, drizzly and fickled. Temperatures within a 20 mile radius of downtown Seattle can vary as much as 15 degrees. Often, visitors to downtown Seattle are surprised by the amount of abundant sunshine and lack of precipitation.

Many factors account for the disparity of weather conditions throughout the region. What are some of these conditions that cause weather to vary from location to location? While there's no doubt that the climate has changed in this region, what will the future be like? Will Seattle's weather be more like Los Angeles or Anchorage? Will Puget Sound be covered by ice, as it was 15,000 years ago or will all our surrounding glaciers melt and disappear? Will climate change bring extremely heavy rain and less snow as some future climate models suggest?

 

Often confused with the wetter coastal Northwest climate, Seattle's annual precipitation ranges from 30 to 36 inches. Almost all of the precipitation falls between mid-September and June as light to moderate showers.

Seattle's marine-influenced weather causes spring to come relatively late compared to inland locations. As winter rains give way to spring showers, cold cloudy days change to somewhat warmer cloudy days. But by mid-June, two or three-day stretches of clear weather begin to occur.

Summer finally rolls into the area by mid-July and for about eight weeks sunny, dry, and mild days predominate. Daytime temperatures usually range between 65 and 75 degrees F. There is the occasional "heatwave", when temperatures might reach the 90s, but unlike other locations, Seattle heatwaves are measured in hours not days. Even on the hottest days, nearing the mid-90s, nighttime temperatures generally fall to 75 or below.

By mid-September the weather starts to the cool. Clear days are replaced with cloudy and occasionally wet weather. By mid-November frost and freezes can occur in the outlying communities. Within the heat island of Seattle temperatures usually range between 35-55 F.

By December sunshine becomes scarce. The short days are cold and wet. Outside of Seattle proper temperatures now range between mid-40s to high 20s. Snow is a rare occurrence an rarely lasts more than a day or two, but just over 15 miles east and west of downtown Seattle daily snowfall totals can sometimes be measured in feet.

Seattle average temperatures measured at sea level:


JanFebMarAprMayJunJulAugSepOctNovDec
High475155596570757570605247
Low363739434853565753464036





Snoqualmie Pass, at 3000' ASL 15 miles east of downtown Seattle:


JanFebMarAprMayJunJulAugSepOctNovDec
High303337435058656659483430
Low222427313641474844372722





Port Angeles, at sea level 50 miles west of downtown Seattle:


JanFebMarAprMayJunJulAugSepOctNovDec
High464851566165696966585046
Low343637404549525249433835td>

Did You Know?