There's just been another thread about water. Is your LO BF or FF? With a BF baby they definitely don't need any water until weaning ireespective of temperature as the foremilk / hindmilk adjusts itself with temperature and age of baby. With FF I always thought you could give it for constipation, thirst I don't know, some people say you can and some not, I'll leave someone more experienced to answer that bit.