We have 5 outdoor cats. One lives up at the house in front of us, And only comes back to eat and drink. She is the mother of the four that live back here. But she doesn't get along with her kids! We bought a heated water bowl for this winter. We got it from the Tractor Supply Co. It has a thermostat and comes on when it gets below 40 deg. F. and shuts off above that. It's big enough that all 5 cats could drink from it at once. It holds about 1 gal. of water. I was surprised how much they drink. We have to put about 1/2 gal a day in it.