Always fun to hear "shorts at minus 10" from the well-blubbered.
My regime:
>18 C - shorts, short sleeve jersey, fingerless gloves, cotton cap, thin socks (above 24 C replace cotton cap with narrow/thin bandana as sweat absorber to prevent it running down glasses)
14-18 C - knee-warmers, arm-warmers or long-sleeve jersey, thin full-finger gloves, cotton cap, thicker socks
10-14 C - roubaix tights and jacket, long-sleeve base layer, thicker gloves, thin fleece hat, even thicker socks
3-10 C - winter (AirBlock) tights and jacket, thick long-sleeve base layer, even thicker gloves, thick fleece hat, thick socks and winter shoes
<3 C - thicker winter (AirPlus) tights and jacket, thick long-sleeve base layer, extremely thick gloves, thick fleece hat, neck-warmer, two pairs of socks and winter shoes (extra base layer and overshoes below 0 C; extra lower layer, waterproof rain jacket and helmet cover below -5 C)
The above is based on riding fairly hard to hard - if riding with someone significantly slower, I often default to the regime below the actual temperature as the muscles won't be generating sufficient heat to stay warm enough.