On a C17... typical family reunification switch. I had a nice, cozy seat next to the loadmaster, someone asked me to switch so they could sit next to the family. I obliged and ended up in the very last seat on the plane, right next to the aft door and the ramp. Little did I know that on C17s temperature spread is minimum 20 degrees between the front and the back and feels more like a 50 degree spread. According to the crew, temp was on the low 40s back there and I wasn't dressed for that. It had to be the most miserable flight in my life, it made me forget all about how uncomfortable a jump seat is. Never again.