<P> The winter wet season normally runs from November through early May . Precipitation episodes in Los Angeles , with a few notable exceptions , are largely caused by extratropical disturbances approaching California from the west or northwest during the winter season . The normal seasonal rainfall measured at downtown Los Angeles is 14.77 inches , of which 92 % falls between November 1st and April 30th . While there is a great increase in rainfall in the winter months , the winter months in the Los Angeles are still frequently sunny and pleasant with mild temperatures . The average highs range from the upper 60 's F to 70 F ( 17 - 21 C ) with cooler overnight lows in the upper 40 's and lower 50 's F ( 8 - 12 C ) . </P>
6 . the primary cause of wet winters in southern california is
extratropical disturbances approaching California from the west or northwest during the winter season