Well, the quick answer is ‘no’. But, in the spirit of Free Your Parenting, I’m now going to tell you why!

Firstly, it’s because breastmilk is 88% water so, as long as your baby is feeding efficiently enough (check that latch!), frequently enough and for long enough at each feed, then they’ll get more than enough water from your milk. This fact has been proven many times, in
many different climates by many different pieces of research.

Secondly, it’s not actually that good to give water to a baby under the age of 6 months:

• Water fills up a baby’s stomach with no-calorie fluid, meaning he won’t be able to fill it with high-calorie fluid, which can affect his weight gain
• If your baby doesn’t feed as much at the breast because of being full of water, you could find you get problems maintaining your milk supply
• Even if you sterilise water by boiling it, and the vessel you offer it to your baby in, it will never be as bug-free as breastmilk is
• In very newborn babies, supplemental water has been associated with increased bilirubin levels, also known as infant jaundice

Once your baby is starting on solids, ideally you offer water alongside meals, but remembering that it’s ‘just for fun until they’re one’. In other words, you’re still not aiming to supplement breastfeeding. Instead, you’re helping your little one learn to drink from something other than a breast. (See Five Tips for Getting a Baby to Drink from a Cup)

NB: The situation is slightly different for formula fed babies. In general, you don’t want to because, again, it’s fewer calories. However, you may need to give them small amounts if it’s very hot weather and there are concerns about possible dehydration.

If you do give a young baby water, then be careful what you use. In the UK, the safest is cooled, boiled tap water. The situation becomes far more complicated when you start looking at bottled waters because you need to make sure that the mineral content isn’t too high for their tiny bodies to cope with.

Edited to add: I have just found this brilliant article by the Rehydration Project, which explains that breastfed babies actually need ^less^ water than older babies or adults because of how breastmilk works. Essentially, breastmilk has very few solutes in it (dissolved minerals in the food and drink we ingest), which means that less fluid is needed for their kidneys to flush them out. So, there you have it, breastmilk really is better for babies in hot weather than water!