I keep 2 yogurt comtainers (empty, with the top wider than the bottom for easy removal) filled near the top (expansion when frozen) with water in the freezer. The containers make big ice cubes. During the hot parts of the day, I put one of the ice cubes in the water of the water bowl for the feral family outside. I add another as the day progresses. The big ice cube melts slowly, keeping the water cool for hours. (P. S.: Newbie here. Glad I found this site.)