I use two methods before I bring them in during the hottest hours of the day.
1. Wading pool; A six foot dia WalMart baby pool, full with 7 inches deep. It cools the feet and they dunk their noses.
2. Misting; Again, at WalMart, found a water mister, connects to the lawn hose. Don't turn-on the hose no more than a drip drip drip rate, the hose will fill and let the fine mist flow and blow. Hang it, from a limb, or under any yard shade, approx no lower than the dog's nose standing height of your largest. He'll found it after awhile, being it will be the coolest spot in the yard and lay under it.
If they have been running or laying out sunning, they'll run to #1 and dunk that nose. It'll take time. Do not rush it. Watch the pool water, change it due to they drink too, gets dirty, mosquitoes breed, algae. Put the water on the plants around that is needing it.
Always, always, take water along when walking the babies. Their feet are burning and tongue is hanging full length =s heat stroke soon.
How did you handle the situation this past summer?