History and climatology tell us that this is not the full story. While sunny weather is frequently associated with Southern California, severe floods have had a significant impact, including major floods in 1862 and 1868 shortly after California became a state. When you also factor in severe droughts, most recently 1987-94, a more correct statement would be that precipitation in Southern California is highly variable, and that rain is most likely between October and April. It helps create operational definitions of drought. Operational definitions of drought help identify the beginning, end and severity of drought, and they vary from region to region, along with climate.
Climatology provides benchmarks, such as the drought of record.
The drought of record is the drought remembered as having the greatest impact upon a region. Reservoir managers, municipal water suppliers and other planners use the drought of record to help them envision the worst-case scenario. But caveats apply .