It would be nice if they made sandals for dogs. I could see Hemi sporting flip flops.
Seriously though, I would just be careful where they are walking in summer. The problem with boots in summer is that dogs sweat through their pads in their feet. This helps cool them down and keep them cool. So putting boots on in summer, while not unheard of is not recommended. Now I have had to put boots in Hemi in the summer when he tore his pads and it was just too hot to walk on anything, but we also didn't go out exercising on the torn pads either. I would just recommend being aware as you are of hotter areas, avoid blacktop, and you should be fine.
Muttlucks does have one call a summer shoe which is supposedly cooler and more breathable however I can not attest to it as I have their winter ones. They are a good shoe. Ruffwear has some as well. However the danger comes in overheating your furry friends.