Below is plot for the Sacramento River, based on tree ring analysis of the precipitation that fell in the river basin. The plot covers years from 869 to 1977. The Green line is based on 30 year smoothing application. The red line is the average over the period. It is possible to see the sever droughts in the 1100s and 1300s, and the smaller drought during the 1930.
A reader asked about the length of the 1930 drought. Here is a chart showing the length of the drought: