The graph above shows all normalized 2010 US hurricane damage (that is, damage estimated to occur with today's coastal development from all past storms, PDF) for all storms that made landfall from August 21st to October 31st, for all years 1900 to 2009.  The graph shows damage that occurred on each day (and the X-axis shows selected dates).  The data comes from the ICAT Damage Estimator.

Even though the current season -- forecasted to be much more active than average -- may appear to be off to a slow start as compared to that forecast, there is a lot of hurricane season left.  September and October account for more than 60% of total historical damage, and if you add in August the total is almost 95%.The most damaging (normalized) storm occurred on September 18, 1926.