I was in Sioux Saint Marie years ago... So I know you get half decent summers too!
You need to work out a couple of things before proceeding with a repair on this Zodiac.
The boat build plate will be on the transom, so you'll have a year of manufacture date to go on. It's important, primarily because it will determine how much time and money you want to spend on something that's possibly only fit for the bin?
I still have a late 1980s Zodiac MkII CGT that has the seams under the lace cuff and row locks. Later boats, the seam was below the water line, so it wasn't subjected to the same expansion and contraction due to heat. More of an issue for boats state-side and in the Med as you actually see the sun!
Temperature and humidity play an important part in the repair. Assuming the boat is PVC (same colour of fabric both sides), then repairs are straight forward. Preparation is key, and you'll need the proper two part adhesive, and to thoroughly prepare the area by sanding, degreasing, etc.
More details here. inflatable boat repair information and procedures about gluing and fabrics
Get some pictures up so we can see progress.