My garage has a floor drain, is heated, and insulated. My garage is free standing and is exposed to the sun if its shining. The garage temp is set and maintained at 60 degrees, but that thermostat is about at eye level. The temp at the floor is in the 35-40 degree range. The floor drain exits the west side of the garage where the ground level is below the drain. That drain exit area is exposed to the sun all afternoon. Up here in the north west corner of IL, the salt infested snow melts off my wife's car every night. After a couple days of cold snowy weather the water in the floor drain freezes. I have to push the salty water/ snow pile out through the garage door every morning after a snow fall.
The floor has a small dip near the drain, but other wise is fairly flat. The water pools near the drain in about a 1" deep 5' diameter pool that captures either the front or the rear of the car (usually the front with a front drive car). There is a smaller diameter pool about 3' in diameter, maybe a 1/2" deep, under the other axle of the car. If the car was covered with snow when it was parked in my garage, there would be considerable more water on the floor. I can push the water out of the door and towards the west side of the drive (the driveway water runs towards the west), but I only get about 3' out of the door before it will start freezing on the driveway. If the sun is out, the driveway will be dry in a couple hours, if it is not sunny, that ice will be there until it melts off, the salt from the road water/snow that was on the garage floor helps some. but is pretty diluted with the amount of water present.
If you have no heat, I wouldn't expect much snow melt, The big chunks will probably fall off the car and stay where they land. If the car is covered with snow, what does melt off and falls on the floor (only because the car body may be warm) will freeze there lands. If you want to keep the floor clean & dry, you will need to clean it about an hour after the car has been parked there, before it can freeze solid. Gene
