Youre right on the point where it may not be necessary, but youll probably want to have something to keep water temps down then. Blowing air across your system will do next to nothing if you dont have an immediate way to remove the heat. Thats why fans feel great but do nothing to actually lower room temps.
So ice bottles if you feel like dealing with it, or a chiller. Even with an external res outside the grow area in a cooler room, its tough to control water temps when your air temps are constantly fighting you. And without cooling or insulation, it doesnt take too long for water temps to match air temps, even with 100+gal capacity.