not much can be done mate, put into corner farthest from entrance and try to elevate the bowl off the ground as much as possbile, or try to insulate around outside with straw or something, i work on farm so always trying to find ways to stop water troughs freezing too hard but lately just had to go early in morning armed with hammer!
and i wouldn't recomend using hot water as, believe it or not, hot water can freeze much quicker than cold water. something to do with the molecules being further apart allowing the frost to turn them into a solid quicker. called Mpemba effect, or something.