Wind sites are rated by class (from 1--7) which represents some average wind power density. In general, wind speeds at height 100 meters above the ground are 20-30% higher than at ground level.

Generally speaking, wind farms would be located in Class 3 sites and above.

Broad averages for the US are shown below:

Class 3 sites and above

Bigger Maps:

Annual average

Winter

Summmer

Reliablity/Certainty in qualitative terms of All Class 3 or high wind power

Alaska is good

Some Regional Potentials:

Oregon

Wyoming

Montana

North Dakota

Minnesota

Michigan

Massachusetts

California

More detailed wind surveys the better:

Detailed Wind resource maps

Scalable Renewable Energy Atlas