2016/17 was BAD (but not quite historic with the March 14, 2017 snow ruining the run at placing each airport on the list except for a 5th place for BWI) - that year ended up BWI 3.0"/DCA 3.4"/IAD 7.3" .
Prior to that mid-March "save" in 2017 BWI had 1", DCA had 1.7" and Dulles also had 1.7".