Annual precipitation averages . Measurable precipitation falls on an average of 127.5 days each year , concentrated heavily from October to April . On average , December is the wettest month , averaging over 8 inches of precipitation , virtually all of it rain . The wettest " rain year " was from July 1889 to June 1890 with and the driest from July 1976 to June 1977 with . The greatest monthly precipitation was in December 2002 . The greatest 24-hour precipitation was on December 27 , 2002 . However , historic 100-year dramatic weather events such as the Christmas Week flood of 1955 and , especially , the Christmas flood of 1964 , which severely damaged the region , may not be reflected in records listed herein . Snowfall on the coast happens only on rare occasions , averaging as of the 1981 – 2010 normals , but only five years during that period received measurable snowfall . = 0.1 in " ; 3 . Year ; 1981 – 2010 ; Probability = 17 % -- > The most snowfall in one month was in January 1907
Christmas flood of 1964
Christmas flood of 1964
Eureka, California