I work 15 hour days and won't be around to make sure their water doesn't freeze. I can't imagine the whole big 25 gallon galvanized waterer would actually freeze solid if it's just getting down to 19 or so. Okay, so maybe it would. I don't know. I'm from Seattle and we just don't see this kind of cold real often. There's snow in their yard and I would think if they get thirsty, they'd eat the snow. I saw one hen doing it today. Do you think that would hold them for the day or at worst, two days? Thanks!