5 miles -- slow and no weather excuse

It was 58 deg/dew pt 46 this morning. Usual route, but 3 minutes slower at 52:41 with the same 137 heart rate. I did the same route in 49:36 @136bpm with 55 degs/55 dew pt (100% humidity) on 15 May. I guess it stands to reason that lower intensity without increasing miles has made me slower.