I don't know what the highest DP I've ever experienced numbers-wise, but it was during a tropical storm in 2001 in Texas. I remember walls having water run down due to the humidity at the height.
There is one for Adams and parts of Lancaster and York. They don't think we see 100 values for 2 consecutive values (the necessary criteria, apparently).
It's absolutely miserable. 85/71 at 11 a.m.