What is one theory that scientists have that might explain why elephants try to avoid rain storms?

Explanation:

Elephants can hear sounds at very low frequencies, even those below the human range of hearing. It's one of the ways they communicate with each other. Thunderstorms also produce low-frequency sound, whether it's a thunderclap or the pitter-patter of rain hitting the Earth.

That would be a working theory.

The answer is reflection.