Compare average sunny days. Or days with precipitation. I lived in Seattle for 5 years and based on temperature alone it is way better than Utah. Warmer in the winter, cooler in the summer. Almost perfect. Until you realize that you haven't seen the sun in 3 months. I'll take Utah and it's cold winters and hot summers over Seattle with it's moderate temperature gray drizzle any day.

July-September in Seattle is perfection. Some day when I'm old and can do the snowbird thing, I'll find my way back up there for part time.