Mill Valley Weather
Mill Valley has a mild climate, with temperatures rarely falling below winter nighttime lows of 43 degrees and summer daytime highs of 74 degrees. Winter daytime highs average around 55 degrees and summer nighttime lows are around 56 degrees. Humidity is mild and averages between 20 and 40 percent.
The rainy season usually starts in late fall and can extend into early spring, with abundant rainfall during the winter months. Annual rainfall is approximately 35 inches, with December, January and February having the greatest average rainfall.
One of the signature summer weather patterns seen in Mill Valley is the fog swirling over the coastal hills and falling down into nearby valleys. Mill Valley can often experience fog even when other cities in Marin County, especially the ones to the north, are very warm and dry. The fog from the coast brings cool and breezy summer weather, with midday temperatures often not exceeding 65 degrees.
Regardless of the fog, May through October tend to be dry months. The Mill Valley Fire Department declares these months as fire season, and prohibits most kinds of outdoor burning, fireworks and barbecues.
Fog streaming into Mill Valley courtesy of Paul MacMahon.
Last updated: 3/26/2008 3:51:05 PM