From The Department of Water Resources California has the most variable weather conditions in the United States, often varying between extremes such as drought and flood. Our ability to forecast variable weather conditions well in advance is a driving factor in how water managers maximize the benefits and minimize the hazards of each storm. Precipitation variability in California is due to our Mediterranean climate, characterized by long, dry summers and mild, rainy winters. Typically, we rely on five to seven significant storms for the bulk of our annual precipitation. (more)