The World Health Organisation's drive to send out a global message that 'breast is best', means that the official line is: even if a baby is thirsty in warm weather, they do not need anything other than breastmilk.
Breastmilk is indeed all a baby needs, and for the first six months, you do not need to give a baby anything else. However, if you are giving another drink, make it JUST water.
This water should be cool, boiled tap water and not mineral waters from bottles. (If you are travelling abroad, seek medical advice about the alternatives to local water in small parts of the world where regular tape water is still a problem.)
Instances where you might offer cool, boiled water could be when you are out and about and it is not possible for you to breastfeed but your child has a tickly cough. Or, when your baby has just begun to try solids and needs something to 'wash down' his food. Try offering this in a sterilsed cup rather than a milk bottle, if you want.
You shouldn't give too much water as this might replace a proper milk feed (breast or formula). But otherwise, sense and instinct will serve you well and as he approaches the age of one, you will see the balance change.
