Why is Seattle called Rain City?

Due to ocean factors, the temperature in Seattle is moderate, and the mountains in the west protect the city from storms. The annual rainfall is 890-970 mm, so it is called Rain City, which is less than some cities on the east coast of the United States (such as new york 1200mm), but it is cloudy for 226 days on average every year, much more than new york's 132 days. As Seattle is located behind the Olympic Mountains, most of the rainfall is light rain or Mao Mao rain.