In Russia we used to race all year round. Only had breaks in spring and fall when it was too muddy. In winter you'd lower the bike, fill the forks and shocks with thin hydraulic fluid, install as soft and as wide tires as you can find, and that's it. No studs back then, they weren't allowed.
It helped to wear thick cotton army pants and coat when you crash on ice, or get run over by another bike. Warm 3-finger army mittens. Stuff a newspaper into the pants' front to keep the cold wind away from the family jewels. Racing at -20C (0F) -- no problem!