I try and stay away from any kind of manure (ex. dog, cat horse, cow, ) wet concrete, hot tar, silica sand, quagmire, fresh cut lawn (unbagged), powder snow, mulched leaves, pulverized black dirt, cat tails, wet gray clay, and anything that contains fertilizer..

Its -5*F here, so it doesnt take long to cool the tracks before running in snow

Enjoy,
Shad