The colder the better. Conditions near freezing are conducive to allow snow to melt a bit and re-freeze on the stalkway on the cornhead; going long enough can lead to a buildup of ice under where the gathering chains run and eventually force them off the drive sprocket. a few years ago I harvested snow covered corn when the neighbour's axial flow had to stop. He actually came over to look in the back of the my F2. It was a weird day--had been a very wet and late fall, we had gotten about 6 inches of heavy wet snow. later, the sun came out, and you could go as long as you did not drive in your old tracks-the snow seemed to hold you upas long as you were rolling. Had to have sunglasses on because of the reflecting sun, had to have the AC on since the cab got quite warm from this reflected heat--and was being passed by snowmobiles--that was a first! Ben.