Exclusively breastfed babies do not require additional water even when it is very hot outside , as long as baby is allowed to nurse as needed. Additional water is not needed for healthy breast-fed babies in a hot climate. Guidelines for offering juice to babies at KellyMom. Milk consumption and hydration status of exclusively breastfed infants in a warm climate. Acta Paediatr Scand Sep;71 5 Breastfeeding and the Use of Human Milk.