page_title: Mount Tamalpais
section_title: Climate
hierarchical_section_title: Mount Tamalpais / Natural history / Climate
caption_attribution_description: Mount Tam seen from Berkeley foothills, in late spring, after a hot day.
context_page_description: Mount Tamalpais is a peak in Marin County, California, United States, often considered symbolic of Marin County. Much of Mount Tamalpais is protected within public lands such as Mount Tamalpais State Park, the Marin Municipal Water District watershed, and National Park Service land, such as Muir Woods.
context_section_description: With its height, various faces, and proximity to the ocean and bay, the mountain contains many microclimates, ranging from cool and foggy in lower ocean-facing valleys with their redwood forests, to hot and dry on the manzanita slopes, cool and breezy at the summit, and shady on the heavily Douglas-fir-forested north slopes near Alpine Lake.
  Annual precipitation around Mount Tamalpais varies greatly from around 27.5–31.5 inches (700–800 mm) in the drier, eastern foothills to about 59 inches (1,500 mm) near the Bolinas Ridge, close to the Pacific Ocean. Both Mount Tamalpais and the Bolinas Ridge force moisture out of the air efficiently, since the air is cooled rapidly as it ascends the steep mountain faces and thus Mount Tamalpais's western part is heavily forested with tall redwoods and Douglas firs. The same fact holds for the steep, south-facing bowl canyon that Muir Woods is located in, with precipitation in Redwood Canyon at around 39.4–47.2 inches (1,000–1,200 mm).
  As in San Francisco, most of the annual precipitation falls during the winter months. During cold, wet winter storms, the mountain also regularly gets some snowfall, sometimes as much as 6 inches (15 cm) overnight, as observed in February 2001, March 2006, and February 2011. The region sometimes gets hit with strong Pacific storms that may topple trees, and bring hurricane-force winds to exposed, barren areas like the Bolinas Ridge and the summit of Mount Tamalpais. In summer, the area gets almost no precipitation, except for fog drip that occurs in Muir Woods, the Bolinas Ridge and the western end of Mount Tamalpais, where summer fog and oceanic breezes are more prevalent. In contrast, the eastern foothills, sheltered from the oceanic breezes and fog, are drier, since the foothills force little moisture out of the air. This leads to the fact that the eastern slopes contain only oak, pine, chaparral shrub, coastal sage scrub, grassland and sparse Douglas-fir forest. Coastal sage scrub also occurs on some of the exposed coastal slopes.
  Temperatures on top of Mount Tamalpais are generally somewhat cooler than places next to the San Francisco Bay or the ocean due to elevation. In summer, however, the top of Mount Tamalpais may actually be warmer than the middle, foggy elevations due to a thermal inversion. The summer fog and breezes make locations on Mount Tamalpais, closer to the ocean, cooler than the blazing hot interior valleys.
caption: From Berkeley, across the bay, after a hot day
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