Yeah, I saw their Facebook post that it was close, but by the looks of your table, we got it. I went back and looked at 84...Dulles got to 35 on 3/31/84. With such an anomalous month, we were bound to break records at Dulles.
ETA: from their Facebook post:
US National Weather Service Baltimore/Washington either 37 or 38. We are just over with the morning low of 39.