I have an outside hutch for Filmore and here in the Pacific Northwest it probably does not get as cold as Nebraska. However, I have had success using two methods over the years keeping a warm spot in the hutch which also keeps the crock of water from freezing.
In my first hutch, I had a plywood floor in one section that I wedged the reflector of a clamp-on lamp with a 15 watt bulb up against creating a radiant heated floor. I could pull the chain on the lamp to turn on and off whenever I wanted; You can experiment with the wattage but don't let the bulb actually touch the flooring; there should be air between the bulb and the wood. Being under the floor and wedged up against the floor not much light or heat escapes.
Currently Filmore's hutch is more spacious and comfortable: He has an inside area with several levels to sit and inside one of the bottom steps I have put an outside light fixture and surrounded it with a plywood step. So when the bulb (now a 40 watt one) is on it radiates heat to the step and hence to the whole inside part of the hutch. This lamp is also on a timer and the plywood is only warm to the touch.
That all said, I don't see Filmore sitting on these warm areas but it is comforting to me to know that he can. BTW the inside of the hutch is filled with straw, something he likes very much and keeps extremely clean.
Dan