We saw condensation—and sometimes the toilet seat was already warm to the touch!
We have a 1930s camp in the mountains, where temps sometimes drop below zero in winter and the bathroom gets chilly. During a cold snap, we noticed the water in the toilet was hot, as if the plumber had deliberately switched the lines. Sometimes the seat is actually warm to the touch! We wonder whether the toilet was deliberately plumbed this way to keep it from freezing in subzero weather.