Just wanted to check my perception so I looked up historical NOAA data for Grand Rapids, MI.

Five year totals (2007 - 2011):

Total number of days with average wind speed >10K -- August (20 days); September (27 days); October (43 days)

Total number of days with maximum wind speed >20K -- August (46 days); September (43 days); October (54 days)

Total number of days with maximum wind speed 15-20K -- August (58 days); September (52 days); October (60 days)

Whether September is windier than August just depends.