Look specifically for anti-fog visors, and save your regular ones for summer use. Depending on the brand, you should be able to find a dark smoke tinted anti-fog (though some brands will only offer anti-fog in clear and/or yellow hi-def).
Be warned, however, that depending on how and how often you clean the inside of your visor, the special coating will eventually wear off, or just become less effective (still, it's WELL worth the investment in an additional visor or two).
I've used my anti-fog visor successfully in temps down to about 37 (and with very high humidity) with almost perfect results. Occasionally I'll have to crack it just a hair at stoplights, as it can fog up with no air movement, but still clears up really quickly.