@edgarblythe,
also, I'm sure you realize as dogs age, their metabolism slows down. However, the being said, with the extreme heat, he might no be getting the steady level of exercise he needs to keep added weight off.
My recommendation is to cut down the wet food (or change over to a denser more nutritious blend) and see what happens after a month or 6 weeks.
Petsmart stores (national chain) carries Blue Buffalo dry and wet food. I'd try a few cans of their varieties of wet food...and see what happens for 6 weeks. I'd try about 8 oz per day..instead of 13 oz. Regardless of whether or not you use BB, I'd try 8 0z instead of 13 oz per day.