Im no genius, but like humans, your not suppose to stay directly in front of a fan, the wind gets you sick over time, dont know how that'll work with a reptile, also u'll just be blowing the same room temperature around.

Im stumpped on any ideas, ME- I'd just provide a lot of water and wouldnt worry about it too much thats not a big temperature difference, a fan is good for good air circulation, just not aimed in the tank, my opinion only