this is taking me back to late elementary school days but I remember some sort of coastal storm in March '94 where at least western areas got a lot of snow (we got around 20" in the Shen Valley).
Looks like DCA hit 36 (hit 38 at my station downtown) - DCA hasn't had a subfreezing high since the 2018-2019 winter. Hell we barely had 30s for highs last "winter".