For Dulles this was the 3rd latest spring freeze since records there began in 1963. Here is the list of the latest freezes (hat tip: Justin Grieser):
2002: May 22
1984: May 17
2013/1996: May 14
1976: May 13
1983: May 11
This morning was just the 4th time since 1873 that BWI recorded a low temperature of 34 or colder this late in the spring according to the National Weather Service. The other times were: May 17, 1956 (33); May 21, 2002 (34); and May 14, 1996 (34)
Outside of the immediate urban core of both Baltimore and Washington, and away from the Chesapeake Bay, most locations in the region dipped into the 30s, with scattered frost.