Although not too common, it can happen if your rat is left in the hot South African sun for long periods of time without shade or water (please note, this is cruelty to animals and action can be taken against you). Your rat might drool, become immobile and unwilling to move, and even lose consciousness. Check the tail – it will be very warm!
What do I do?
Place your rat into cool water, keeping the head above water, or wet its fur with cool water using a cloth. You can try feeding it a sports drink/water with a syringe (no needle please!) if the rat is conscious. Get it to the vet as soon as possible, as complications can include organ failure, blood clotting, and even brain damage.
Rats cannot sweat like humans can. Keep their cage out of direct sunlight, and if temperatures soar then keep a fan blowing in their direction. You can also freeze water in a plastic bottle, and put this in the cage (ratty air-conditioner).