The climate in the Anderson Valley appellation is tempered by cool marine air. Steep hills and mountains surround rolling to nearly level alluvial terraces. The dominant natural vegetation is a mixed forest of Coast Redwood, various native oak varieties, and Douglas-fir. Elevation ranges from sea level to 2,500 feet (760 m). The average annual precipitation ranges from 35 to 80 inches (900 to 2000 mm). The average annual temperature is about 53 °F (12 °C), and the average frost-free season ranges from 220 to 365 days. Towards the coast the summers are cool and moist with frequent fog, while the interior Anderson Valley proper features a warmer climate during the day, with daytime highs in excess of 100 °F (38 °C) several times per year, but diurnal temperature swings consistenly 40 to 50 degrees. In the southeastern end of the Anderson Valley near Boonville, frost is guaranteed during the growing season; only the frequency varies.
Visitors to the Valley should come prepared for cool evenings and warm days. Locals dress in layers year round.