They really look like that pic from Borneo Exotics with the frog inside, right?
According to my experiments from last year, N. Hamata can take up to 28~29c but above that they will start to lower their lids. The problem for me is that were I live night temps can be up to 26c in the worst weeks... even after lowering their night temps with ice packs they ended up being stressed.
When the tank is close to the AC it can keep the temps inside around 19c, hope that is enough, at least they grow with those temps in spring and autumn. The things we do for these plants.
I tried a few times to grow N. Burkei without any luck, but I really like it. And attempting N. Burkei x Hamata was a disaster for me I wanted them because of their darker coloration, but the Ventricosa cross had been way easier in the end.