I was in Philly in the Mid 90's so was not around here to remember but checked the NWS stats and the highest Min MDT recorded in recent times was 81 in August 2011. So probably more localized if Mid 80's. They did have a day, July 1995, where it got down to 80 for a Max Min. The record is August 9th 1900 @ 83. In 1991 MDT was over 100 3 out of 5 days late in July.