Please keep in mind that the poo output reflects what has been going into him 1-2 days before. It takes about a day for food to pass from one end to the other.
However, it is not a good idea to overfeed fresh food and fruit in hot weather because piggies don't have sweat glands nor do they pant like dogs. They regulate their body temperature via increased blood flow close to surface areas, especially the ears.
It is much more effective to offer a good supply of cool, drinkable water (not ice cold although you can add crushed ice if you are out all day) and to keep the room they are kept in as cool as possible but not up their veg intake as that can cause diarrhea.
Only if you cannot guarantee a supply of drinkable water all day or when you travelling, we recommed to leave a large chunk of cucumber in the cage/carrier as it holds the coolness in the core for longer and provides a non-drip supply of edible fluid.
The temptation to overfeed watery veg and fruit in hot weather