Cold weather clothing
Below 65°F (18°C) I make sure my knees are covered. This is particularly important as we grow older. Many riders suppose that since they can walk around in shorts at that temp, they can ride in that temp too. The problem is that wind-chill (created by cycling) will pull the heat off the knees. The alternative to wearing tights is a heat salve that racers use.
I will cycle in temps dropping to -5°F (-20°C), but as the temp drops, my clothing requirements change accordingly.
50°F to 65°F (10°C to 18°C) = Helmet, short-sleeve cycling shirt, light cycling shell jacket, fingerless cycling gloves, cycling shorts, lycra shorts, socks, cycling shoes
35°F to 50°F (2°C to 10°C) = Helmet, long-sleeve cycling shirt, wool vest, light cycling shell jacket, long-finger cycling gloves, cycling shorts, lycra tights, socks, cycling shoes
10°F to 35°F (-12°C to 2°C)= Helmet, balaclava, long-sleeve cycling shirt, wool vest, down jacket, light 99-cent wool gloves inside long-fingered cycling gloves or leather winter mitts, cycling shorts, lycra tights, cotton trousers, two pair of socks, cycling shoes, neoprene booties
-5°F to +10°F (-20°C to -12°C)= Helmet, balaclava, long-sleeve cycling shirt, one-piece Ski-Doo(R) suit, 99-cent wool gloves inside leather winter mitts, cotton trousers, two pairs of thermal socks, cycling shoes, neoprene booties