Well the "og days? of August are here and gone, on many days, "arly and late? are about the only times a dog can be exercised. Even then, there should be plenty of water around for dog, if necessary. Onetip on water is to put a little chlorine bleach into the water tubs. The formula is about 9 drops per gallon to kill off all biologicals. The water will keep better and will less likely draw the green scum, but will still need to be changed every five or six days as the dogs muck it up and it finally becomes stale.
You can carry water with you too, but, be careful. Dog can become to reliant upon you and you thus teach them to come the whole way back frequently, which can detract from their work and concentration in the field. It is much better for them to find water on their own, even if it is from tubs and pools that you provide.
Finally, many dogs will benefit by a summer haircut. It really does help a long-haired dog working dog to dissipate body heat and feel more comfortable. Not too short though, dogs can be sunburned if cropped to close. But all dogs need to acclimate to the summer heat. Work them into warm conditions gradually. Be very careful in this regard with dogs that live in air conditioned quarters as they are less likely to acclimate. Keep your dog safe in the heat!