As a resident of the DC Metro area, I second Danny's warning. The 2012 event brought down more tree limbs (from apparently healthy trees) than any of the several hurricanes we have experienced here---combined! We didn't lose any trees, but it seemed close. So take warning. Treat a Derecho just like a Hurricane and take a look at Wildman's recently posted check list.

Thing I ended up not having at the ready---a chain saw. . .with a sharp chain (really important)!