More important than wind speed is reliability.

 www.nrel.gov/wind/usmaps.html

This map shows the percentage of U.S. land area having an wind resource class of 3 or above on average per year. Wind power class 3 is characterized by winds ranging from 6.4-7.0 m/s. Seven meters per second is roughly equal to about 14 or 15 mph, which corresponds to the minimum average wind speed needed to support a large-scale commercial wind farm. From this map, we can see that the greatest potential for wind power development lies in the Great Plains region of the midwest.

Although possessing a relatively small percentage of land area meeting the minimum wind speed and reliability requirements to support wind power development, California has taken significant steps in that direction. According to the California Energy Commission, California currently produces 30% of the world's wind generated electricity in three of its wind farms: Tehachapi, Altamont Pass, and San Gorgonio. These facilities are also responsible for about 1.27% of the state's total energy production.