How much sun does Seattle get? The short answer is 3.3 on a linear scale where Yakima WA is 4.1, Los Angeles is 4.9 and Las Vegas is 5.7. Germany, the biggest solar market in the world, is generally less than 3. That puts Seattle at 67% of Southern California, better than you might have guessed, and better than Germany.
The long answer is that there is a lot of data available on the internet for folks who like to look things up for themselves. A good starting point is NREL, the National Renewable Energy Lab. They have been researching, collecting, archiving and displaying this kind of information for many years. The numbers above for example came from their archive of 30 year averages for 1961-1990. Other NREL resource links lead to a variety of sources, for example an interactive map called Solar Prospector where you can zoom in to your exact location and choose from a variety of data configurations.
