WX data for DCA, which probably wasn't as windy as IAD:
13 Nov 03 (all in mph, not knots)
13:51 EST N35 G47
14:51 EST NW31 G48
15:51 EST NW23 G37
16:51 EST NW24 G39
17:51 EST NW24 G32
I live across the river from IAD in Maryland and my electricity was off for almost three hours during that time period.