Monterey Bay Climate and Weather
Monterey Bay experiences a mediterranean type climate with cool summers and moderate winters. Rainfall averages 19 inches per year and falls almost exclusively between October and May. The seasonal shift between the dry spring/summer period and the wet fall/winter period is governed by the position of the northern hemisphere storm track and of the North Pacific high pressure system. This seasonal shift also governs the prevailing winds. In the winter, frequent storms pass through the area resulting in strong winds with variable direction. The spring transition, in March or April, marks the beginning of several months of predominantly strong winds from the northwest. These are intermittently interrupted by periods of several days duration when the wind slackens and may come out of the west or south. In particular, a phenomenon known as a southerly surge will suddenly reverse the wind direction from blowing out of the northwest to coming out of the south, as it propagates northward along the coast. The fall transition typically occurs in September and is a time of calm winds and sunny weather before the onset of the winter storms, usually in November. There can be significant year-to-year changes to the "typical" annual cycle, some of it associated with the El Nino – Southern Oscillation (ENSO) cycle and/or the Pacific Decadal Oscillation (PDO).
Due to the proximity of the ocean and coastal mountains (hills), there is considerable variation in the weather over short distances in the Monterey Bay region. For instance, frequently in the summer Pebble Beach will be foggy, while Carmel Valley is experiencing bright sunshine. Often you will see distinct differences in the wind speed and direction over the Bay. For example, when the winds are out of the northwest, the northern part of the Bay will be sheltered and will experience light winds, while the winds in the southern part of the Bay are stronger, and even stronger yet outside the Bay to the west.
Due to daytime heating, the wind varies in speed and direction over the course of the 24-hour day. The acceleration of winds directed down the Salinas Valley in the late morning and afternoon is particularly evident on sunny days, and can be seen in the animations. You will see this effect most pronounced inside the Bay, with less diurnal variation as you go further offshore.
You can learn more about the climatology and meteorology of Monterey Bay at http://www.mbnms.nos.noaa.gov/sitechar/clim.html