s in the Santa Cruz Mountains. The Santa Cruz Mountains have a Mediterranean type climate typical of most of California, with the majority of the annual precipitation falling between November and April. According to the
National Weather Service, this totals more than annually. Heavy summer fogs frequently cover the western ocean-facing slopes and valleys, resulting in drizzle and
fog drip caused by condensation on the redwoods, pines, and other trees, which sustains the moisture-loving redwood forests. Due to a
rain shadow effect, precipitation on the eastern side of the range is significantly less, about a year. Snow falls a few times a year on the highest ridges, and more rarely the higher valleys receive light dustings. The
National Weather Service's cooperative weather stations in the mountains have included
Black Mountain 2WSW – average annual rainfall , maximum annual rainfall , average annual snowfall , maximum annual snowfall ;
Los Gatos 5SW – average annual rainfall , maximum annual rainfall , average snowfall , maximum annual snowfall ; and
Wrights – average annual rainfall , maximum annual rainfall , average annual snowfall , maximum annual snowfall . No temperature records were kept at these stations. The Santa Cruz Mountains are subject to sharp
diurnal temperature fluctuations. The highs and low within a 24-hour period are ~20–30 °F apart on average but can be as much as 50 °F apart during heat waves depending on location. There is also considerable variation in temperature from day to day in both summer and winter with shifting wind directions, and fluctuations in the degree or marine influence. Average winter highs range from the low 60s °F (~16–18 °C) Average Winter overnight lows are a function of topography and can vary significantly, from an average low of in the thermal belts above the inversion layer where cold air can readily drain off the slopes.
Thermal inversions occur primarily during the Winter when cool air sinks and gets trapped in the valleys at night, often leading to frost and occasional freezes. Higher elevations above the inversion layer usually stay mild with frost being a rare occurrence. The
USDA has recently re-classified the hardiness zones for the higher elevations as USDA 10a to 10b to reflect the lack of frost at those locations. However, while the higher elevations are less prone to frost, they are also more likely to experience occasional snow accumulations. The valleys in contrast are rated USDA 9b with some locations as cold as 9a due to the lack of cold air drainage. Summer temperatures regularly reach highs in the 80s °F (~28–30 °C) with nighttime usually in the upper 40s to lower 60s °F (~9–18 °C) depending on elevation, distance from the ocean and degree of marine inversion present. Summer weather is dominated by a persistent
marine layer that can vary in depth. When the inversion layer drops below 300–500 feet, the higher elevations are deprived of marine influence and will often be subject to intense heat waves with daytime temperatures in the range and extreme low humidity with elevated overnight lows that offer little relief from the heat. Such conditions can lead to fires that can occur even before the official State of California fire season starts. Examples of such fires include the 2016
Loma Fire, the 2009
Lockheed Fire and the
Summit Fire in 2008. == Recreation ==