Putting the battery and receiver in balloons is easier, then just ziptie the neck around the wires. You can buy hardcore off road/mud air filters that have a cover. As long as you aren't trying to plow through standing water or slush, it shouldn't be a problem though.
Keep in mind that when snow/slush/ice cold water hit your engine, it could cause serious issues with tune to say the least. In extreme cases, if the engine is running overly hot, ice cold water could cause it to crack.
I run in the winter though. I try not to run when it's below 25F or so, mostly for my own comfort. Batteries die far faster in cold temps than warm, so you have to keep mind of that as well.