For winter snow running, theres the tuning issue and the snow issue. The tuning issue can be fixed by the obvious, but don't tune to lean.
The snow issue is a little more extensive. The snow melts and turns into water (duh...), when this happens, it tends to get into your battery packs, receiver and servos. You can put ballons around all of these parts and ziptie the balloons shut to protect against damage. Believe me, it's worth the time. 2 servos and a torched truck later (hit a garage doing 40 with my xxx-nt), i figured out how imparitive it is to protect against water.