Yup, the cooler temperature of the toilet is the first thing that leads the cats there. The temperature of the water is also cooler in the toilet than the one in their drinking bowls if the bowls are located in an area where there is little air movement.

But not a good idea to let the cats drink any water from the toilet bowl or floor. Who knows if your floor have been thoroughly cleared of the shampoo or soap leftovers. And some people use the air freshner spray after their "big business", that too can leave some undesirable contaminants in the water on the floor if any.

wooz....