4 hours Z2 in ridiculously nice weather for December 27th in Massachusetts. The high was something like 50 degrees! I had wool socks, a cycling cap, glove liners with normal half-finger gloves, leg warmers and a warm base layer under my jersey, and that was all the thermal gear I needed. I passed a lot of recreational riders in tights and full-on jackets. For high-40's, low-50's!? Mystifying.