If you only get to mid 20's, then keep your fresh water tank full.
If you are connected to shore power, they make special outlet plugs that turn the power on when the temp gets below 35 degrees. Use one outlet to power up a 100 watt incandescent bulb in the wet compartment and another one to power up a small electric heater inside the coach. Make sure that the light bulb is in a safe position and away from other items and make sure that your electric heater is in a safe location. Maybe on your cook top.
Obviously you will want to watch the weather and if you see it getting much lower, you can add another light bulb in the wet compartment.
The above works for us when have camped in -6 degree weather. We have never had the fresh water tank freeze no matter what the temperature has been.
