I have to agree and sympathise with the original poster that Celebrity has to improve their tender service during hot weather.
We just returned from the Edge and had tendering in Portofino and Cannes. This was using the Edge's own tenders.
In neither case was there any noticeable AC on the tender. I could see an AC unit, but as far as I could tell it wasn't running. In Portofino the tender to ship I think was shorter so they seemed to be running the tenders fairly frequently. It was hot on board, but the tender didn't sit around and the trip was short so it was manageable.
In Cannes it was 35C/95F so it was a hot day. We got to the tender and hopped on thinking based on our experience in Portofino it would leave quickly, unfortunately we ended up sitting on a hot tender with no AC and limited to no ventilation until every seat was full. About 20 minutes or so. Honestly not something I would like to do again. Why Celebrity wasn't running the AC, I don't know? We had planned on going back into Cannes for dinner since we were in port till late, but neither my wife or I was willing to go through the tender experience a 2nd time.