Chapter 16 - North Pacific Coast

The North Pacific Coast region is known for being wet.  The region has the greatest average precipitation in North America.

Unlike the North Pacific Coast, Simi Valley has far less rainfall throughout the year.  On average, the wettest month of the year in Simi Valley is February when around 4.5 inches of rain falls.  On the other hand, Seattle has three months a year (December, January and February) with more average rainfall.  Between May and September in Simi Valley, there is usually less than half an inch of rainfall.  In Seattle, there is never a month with less than a half inch of precipitation.

Sources:
Regions and Landscapes of the United States and Canada (p325-325)
Seattle Wikipedia (http://en.wikipedia.org/wiki/Seattle)
Simi Valley Wikipedia (http://en.wikipedia.org/wiki/Simi_Valley,_California#Climate)