Ed,
I've done an number of these "last ride of the year" deals. Once in you're part of the world I made an October ride from Mineral Point to Eagle River and back. The "way back" part it was chilly, but sunny. I remember pulling over by the roadside periodically, laying in the sun to soak/store up thermal units then carry on

. Another fall I visted some friends in Stevens Point and headed home late afternoon. Stopping for gas, my face was so cold I literally couldn't form words with the attendant. Wisely I reversed course, spent the night and completed my pilgrimmage the next day.
I've always felt that late season 55dF is 'thinner' than mid season 55dF. As driving into a deep shadow takes my breath away. Must have something to do with ground temperature, angle of the sun or something. BTW, I have never learned from experience, I'm sure it will happen again, and again

.
jh