The fall migration has started (Ospreys seem to start mid-August) and will run until the end of November. Hawks are more likely to fly west when there is a light breeze from the west and they concentrate by the lake when there is a northerly component to the wind. They are also far less likely to migrate in rain or completely overcast days, as many rely on thermals created by the sun warming the ground.
If there are several days in a row with rain or strong east winds followed by a clear day (with just enough cloud cover to make spotting them easier) with a north-west wind, get yourself to a raptor watch.
