I do most of my ATV driving in weather very cold, from - 10 degrees on up .

This is what i have on my ATV.

#1 HAND AND THUMB WARMERS ( They work great when your gloves are wet.)
#2 ATV hand gauntlets that go over your handle bars to keep the rain, wind and snow off of your gloves.These are very important for winter driving, most of the time i do not need gloves when these are on.
#3 Hard box on the back to carry food and water and extra supplies as i usually travel up to 60 miles per day.
#4 Chain saw,, If you drive in early NOV. or DEC. .snow storms will knock down many trees and you will have to clear them..
#5 2 gallon gas can. I have never had to use it but when i do not bring It i seem to worry about gas when i am 40 miles from no where and it would come in handy if i need to start a fire in a hurry.
# 6 100 ft. rope in case my winch is not close enough to a tree
#7 Food and water and first aid supply in case i need to help someone in the woods..
#8 Seat warmer by Cabelas,, It stretches over your existing seat and has a on/ off button. It may sound like a little over kill but you can drive in 10 below weather for 8 hours and laugh at the weather.
#9 Last but not least my cocoon poncho, This poncho is quiet , huge, has a zipper for quick on and off. you can snap it on your ATV but i do not need to. It has weight on the bottom so it just flows over the ATV and you will get engine warmth. When i wear this i can wear jeans or other light clothing as this product will keep you very comfortable i the most undesirable weather.