After three consecutive dry years, a full 58% of California is experiencing what is known as an exceptional drought. California, like most states west of the 100th meridian, is arid, with average annual rainfall around 30 inches or below. But the term “average” is misleading, as rainfall varies dramatically not only from the northwest corner of the state to the southeastern desert, but from one year to the next. And in years with little snowfall or rain, drought strikes hard against California, the state that supports the largest population and economy.