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One of the defining characteristics of San Francisco Bay Area weather is the never ending waves of fog. Within the United States the three foggiest regions are the Pacific Coast states, New England and the Appalachian highland region. On a global scale, both poles of the planet and the tropical highlands of Central and South America boast a significant number of days with fog. There are many types of fog but the summer drifts and banks of advection fog along coastal California are those that most frequently visit Berkeley gardens. This advection fog is formed because the surface waters near the coast are much colder than offshore Pacific surface waters. When warm, moist air above these offshore waters is transported by westerly winds over cooler coastal waters, the air temperature drops to dew point and fog is produced. How far inland the fog travels is dependent on the strength of these onshore breezes, local topography and how quickly the fog dissipates when it meets the drier inland atmosphere. When atmospheric highs create offshore breezes, our coastal fogs disappear, temperatures rise and air quality goes downhill. 
Sequoia sempervirens, our coastal redwood of California and southern Oregon depends heavily on fog drip for survival. Fog moisture is collected by its needles and branches, some of which is directly absorbed by the foliage while much of the remaining water drips to the ground, where some is absorbed by the tree's shallow root system. Without summer fogs our redwoods could not grow to be the tallest conifers in the world! Under this dripping redwood canopy ferns, mushrooms and banana slugs go about their daily business. In the Namibian coastal desert in extreme southwestern Africa, summer advection fogs bring life supporting moisture to the plants and animals of an otherwise extremely dry environment. Namibian sand beetles harvest moisture from the fog by holding up their wings, collecting condensation which runs down into their mouths. The Namibian dune beetle digs narrow trenches in the sand perpendicular to the fog carrying winds. Moisture condenses along these trenches from which the beetle collects the life saving waters. Neighboring Welwitschia plants collect fog moisture through their large leathery strap-like leaves. Without these summer fogs many animals and plants could not exist in the desert environment. High in the rain starved mountain villages of Chile, moisture is collected by stringing large nets across nearby fog laden slopes of the Andes mountains. This moisture drips, runs downward and is collected in barrels. A recently constructed series of fog nets now harvest up to 63,000 quarts of water daily. There are of course a few drawbacks to our life sustaining fog. Auto and airplane fog-related accidents are not uncommon during the foggiest months of the year. Roses and other susceptible plants often suffer from foliar diseases when exposed to excessive humidity and warm temperatures. And lest we forget, unrelenting fog has been known to adversely affect the disposition of Mediterranean climate-loving people. To the chagrin of many friends I pray for fog on a daily basis. Perhaps it's my Scottish or Norwegian ancestry that enables me to be refreshed and renewed with its daily dosages. Its white banks of moist air moderate daily temperatures and bring moisture to the ever dry plants and animals of our arid landscape. These drinks from the sky support life in a quiet and nurturing environment. Fog is beautiful and life giving! — Ernie Wasson
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