Joined: Feb 2013
Posts: 1,472
Likes: 11
From: Near St. Louis, Missouri
Bikes: Giant Defy Advanced, Breezer Doppler Team, Schwinn Twinn Tandem, Windsor Tourist, 1954 JC Higgens
I believe in the old "covered knees below 60 degrees" adage. I'll cheat a few degrees if it's going to warm up quickly.
Also remember that there's a third option: knickers. They keep the knees warm, but let the lower legs cool off.