Also freezing water in the bowl provides cool water as it melts. Never keep the windows open far enough that your dog can jump out. Again the Aussie's instincts may overwhelm him causing him to want to chase or catch a passing car, dog, cat, bicycle rider etc. Window guards are available that allow more air. Never leave your dog in a parked car on hot days.
Temperatures rise quickly even with windows open.
Provide cold damp towels for him to lay on to help reduce heat stress. Teach your dog the wait command and make sure you have a firm grip on his leash before giving him the command to get out of the car. Use an unusual command that others would not think of using if they were to try to steal your dog. The Aussie is a herding dog and because of their strong herding instincts additional safety precautions must be taken to insure your new family members safety. Your Aussie will start the bonding process almost immediately.