I would run it. The type of fish were talking about are used to some water temp fluctuations now if your dealing with trout that could be a different kind of monster those fish are picky. These are not your normal aquarium fish. I always keep mine going through that kind of rain to help keep things mixed up good and I have not had any issues as of yet.
You don't just wake up great one day. That's not the way it works. What you get out of life is directly what you put into it. So if you think you can cut corners skip workouts and deny your body the fuel it needs think again! We've got work to do!!