Wind assessment takes place at a number of different levels: consulting a wind map, obtaining previously measured data, and taking your own measurements. The cheapest and easiest way to assess your resource is to consult a wind map. Wind resource maps of your state are available at the US Department of Energy WindExchange.
It is important, however, to remember that wind maps are seldom detailed to the level of individual homesteads and there are many factors -- such as hills, buildings, and trees -- that may further cause variances from the map. Nevertheless, it is a good place to start to give a general idea of your resource and do some basic economic analysis.
The next step is to obtain data that has already been measured by other groups in your area. State governments frequently have weather stations around the state in which they receive wind speed data. Airports also keep track of wind speeds in their area.
Finally, you can measure your own wind speed by installing a device called an anemometer. Some state energy offices have a loan program that allows you to rent an anemometer and data loggers to record your wind speed data. Contact your state energy office to learn more. You can verify that the data you collect is consistent with long-term wind. Site-specific measurements using anemometers are considered by some to be the most reliable estimates of the wind resources for a project. However, they can be quite costly and require from one to several years to complete. Other methods also exist where large scale computer weather models are created to extrapolate wind conditions at a specific site from historical data. Many times these computer models of a site's wind resource can be less expensive than taking meteorological readings for a year or more.