Here is an image of Offshore Wind Potential from NASA's Earth Observatory:
It looks like there is significant seasonal variability. It will be interesting to see how many of these projects get started. As I have posted in the past, these projects may not be viable in some locations due to high start-up costs. These costs have not stopped all projects however. Delaware will have the first offshore project in the US. In addition to Delaware, it appears that numerous other states are pursuing offshore wind (examples:GA and MA).
Note: Here is an excellent site from Oregon State depicting wind potential. By clicking on the map you can view different regions by month.