Since I was trying to find the answer to this myself, thought I would share what I have learned. It has suddenly gotten quite hot, Nate’s room is around 26 degrees and he has already woken twice tonight. So based on what I have read online and in one of my baby books these are some ideas, but please note that I am not a professional so if you don’t feel comfortable with any of these suggestions please don’t do them.
1. Strip baby down to just a vest or if very hot just a nappy.
2. Cool baby down with a washcloth/flannel that is luke-warm-cool, not too cold as it will shock baby.
3. Strip bedding down to bare minimum and use cotton where possible as its breathable.
4. Remove things like bumpers, cot tidies etc and anything stopping good airflow into the cot.
5. Open a window or put a fan on but make sure baby is out of direct contact with cool air.
6. Give baby some cool water to drink or a cool bottle of milk, make sure baby stays hydrated.
7. If breastfeeding you may want to put something in between the skin like muslin or a cool cloth as skin to skin contact can be very warming.
8. There is a water spray called Magicool that you can spray on the face to help cool down, although I don’t know how suitable that is for babies.
9. For older babies/toddlers you can freeze fruit and let them suck on them. It can get quite sticky though.
Hope these ideas have helped.