I don't understand why you would bring the plants in for just the night. Is that when it rains? I'm assuming that night time is coolest, as the sun is away. It would make more sense to me to take the pot in during the day when the sun is strongest.
If you are getting lots of rain, then the fan might be a good idea. I do think, however, that the best place to start would be to set up some sun (and rain) shade. A fan can be useful for drying overly wet semps quickly, but please be careful of electrical shock, especially in damp or wet conditions.
A fan to lower the temperature will not do any good if the plants are in the sun. The sun will heat the plants faster than the fan can carry the heat away. The fan would be useful in cooling and drying plants in shade.
IMHO
