Always make sure there is plenty of water and areas where cats can keep cool.
If an animal becomes overheated they will act in a strange way cool them down with a cool towel and put them in a cool part of the home.
When the cat has recovered from heat they will eat a little and probably drink water, milk is not recommended since this is not designed for cats.
Plenty of fresh air through the home can help cats will lie on cool surfaces to keep cool.
SallyGilson 