If there is plenty of shade in your gardens, I think you can safely assume that if your cats go out, they are sticking to the shade.
My younger cat does, while the elder goes out in the early morning and late evening, spending the hottest hours of the day lying on the bathroom floor - the bathroom faces north-west and has a stone floor.
I have made sure that the usual indoor and the outdoor water bowls are kept full and supplemented by a saucer of water for the hedgehogs, as they cannot reach into the bowls and a old metal basin with three inches of cold water,
Most dogs have the sense to find a cool spot indoors, but they should certainly only be taken for walks in the early morning or when the temperature falls in the evening.
Plenty of water readily accessible is necessary for us all right now. An indoor fan is a good idea too, if your rooms face south.
Scottish political mess. Is Devolution working?