I went running with my favorite, and most reliable, running partner this morning - my dog Meeka. (No offense to my human friends.) She is with me for every running session, year round. I wrote a story about running with a dog in winter and running in summer requires as much forethought and caution as winter running. Maybe you, or someone you know, could use a few tips for running with your dog in the summer.
Meeka on her trail run this morning
Avoid the heat: I tend to run as early in the morning as possible to avoid the heat of the day. If I can't avoid a hotter part of the day, I try to run somewhere that has shade or where she can take frequent dips in a lake or stream. I watch her panting to be sure it doesn't turn from normal and rhythmic to extreme and labored with her tongue hanging out the side of her mouth.
Slow the pace: Just like humans, dogs tend to slow down when it gets too hot. This is particularly true for really furry or black dogs.
Watch the paws: A dog can blister their pads if you run them on hot concrete or asphalt. Run when it is cooler or use booties. Also, people that run dogs on sandstone rock (ie Moab-ish rocks) should consider booties.
Carry fluid for Fido: If you can't run where there is an easy source of water for the dog (near a lake or a stream) then carry extra water for the dog. Know that dogs can get Giardia from water sources. There is a vaccination that prevents Giardia, so talk to your veterinarian to see if this is something your dog needs.
Watch for snakes: If you run trails, watch out for snakes. Keep your dog on a short leash and keep an eye out for snakes lying under a bush, getting ready to sunbathe. Carry Benadryl or a similar antihistamine for the unlikely event of a snake bite (for you or the dog). Talk to your vet about the proper dosage for your dog.
Control your dog: The trails are much more crowded in summer months. If you have access to voice control trails (leashes are not required), be sure your dog really does respond to voice commands. With or without a leash, do not allow your dog to approach another dog without asking if the other dog is friendly or not. Keep your dog from charging or jumping on other dogs or humans. On the human side, I know it might be hard to believe if you are a dog-lover, but some people don't like dogs or they are very fearful of dogs. There is no need for confrontation.
Light on the leash: Teach your dog to walk and run on a lead without pulling. Constant pulling can cause arm or neck injuries for you and can damage the esophagus of your dog.
Pick up the poo: Carry poop bags for your dog's waste. No one, including other dog owners, wants to wade through piles of poop on their favorite trail, neighborhood or park. If the smell puts you off, carry a ziplock bag so you can store the poop bag(s) in a relatively smell-proof location until you get to a trash can. When I run in the city, I know where all the dumpsters are located so I can get rid of the bags quickly.
There are probably some tips I'm missing here, but it's a good start. If you need to do a long run in extreme heat, it's probably best to leave your dog at home and plan a swim for the dog, and maybe you too, when you get back from the run.