California has a Mediterranean climate, with hot, dry summers.  Pacific storms bring precipitation (rain and snow) to California during the winter.  Because of California’s unique geography, moisture flows inland from the Pacific Ocean and condenses (squeezes together, becomes denser) as it rises up the west flank of the Sierra Nevada Mountain range.  This orographic lifting (the cooling of air as it is lifted) causes clouds to form as the moisture cools, and precipitation in the form of rain or snow is the usual result.  California’s water resources primarily originate (begin) in the Sierra Nevada and other Northern Californian mountain ranges.  As winter snows melt, they form the headwaters (small streams that start a river) of California’s northern rivers.  These rivers then flow into lakes or out to the ocean, evaporate (change into a vapor, or gas), and the process starts again.  Since the clouds drop their moisture on the west side of the Sierra Nevada, the east side is in a “rain shadow” and experiences arid (dry) conditions.  This is a reason for the deserts of eastern California and western Nevada.

Check a map of California to see where all of these cities are located.  Are they in northern, central, or southern California?  Check their elevations (how many feet above sea level, or asl).  Are they on the coastal plain, in a desert, on a mountain, in an inland valley?  How does the elevation affect their climate?  What kinds of plants and crops can grow there?  Can the plants grow there year round?  Why do people live there?  These are all questions geographers ask themselves when they look at data.  Make a graph over a month or longer, for one town or several, and notice the change in temperature.  Why are some cooler and others warmer?

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