The Mediterranean climate of the Big River Basin is characterized by a pattern of low intensity rainfall in the winter and cool, dry summers with coastal fog. Temperatures range from 20 to 100°F. Mean annual precipitation for the basin is about 50 inches and varies from about 38 inches at Fort Bragg near the western margin of the basin, to over 80 inches at the northeastern edges. Rainfall maps for the basin indicate that although annual precipitation generally increases as one moves towards higher elevations along the north and east parts of the basin, there are areas in the Inland Subbasin that are considerably drier (GMA 2001a). The North Fork drainage is noticeably wetter than either the South Fork or headwaters drainages. Precipitation is highly seasonal, with more than 97% falling between October and May. Snowfall occurs occasionally in the higher elevations of the basin but rarely accumulates. Snow does not have any appreciable effect on the basin’s hydrology.