Here's a fun one - the last time that DCA (current airport location) had a consecutive week below freezing with at least 5" of snow on the ground was...never.
1989 had a longer streak, but less snow on the ground (2-4")
1979 had a similar streak, but some of the days had 4"
1961 had a 13 day stretch where it hit 33 twice (3-9")