All Ur baby needs is formula or nursing. That's it. Don't give Ur baby water. And always speak w Ur pediatrician when u have Qs.
There has been recent info in the uk about not giving water after a baby died having had too much. If you're formula feeding then baby is def going to get enough water, not so sure about bf. Speak to your midwife or health visitor about how much is safe to give. You will be able to smell if he is dehydrated, there is a distinct smell on their breath (which you will become all too familiar with over the years!) It's a kind of sweet smell, it's hard to describe, but you will notice it if it's there. Try not to worry too much, I've been putting my little man (6 days old) in his bouncer more than I would normally at this age just so we're not cuddling him too much and he's currently asleep in just a vest with his shawl to keep the chill off. We're suffering in Scotland, so it's probably pretty bad for you guys down south!
He is having a lot of milk so that's good then just worried in this silly weather
Give him milk for hydration