Is it possible for water to freeze in inside house plumbing if the house temperature is 50 deg. or above?

We're going on a winter vacation and I want to turn our house thermostat down to around 55 deg. (in Michigan) However, I've had people tell us we risk having our water pipes freeze at that level of inside air temperature. This doesn't make sense to me, and the people can't explain how the freezing would take place, only that they've heard of this happening.