If you get struck by lightning depletes HP from your characters. If you have a penchant for pain then that's good for you because you can definitely receive prizes for surviving bolts of lighting. Below are the information's of what you will get in the number of bolts you dodged and struck.

Dodge Lightning
5 Times will get you 2: X Potions
10 Times will get you 2: Mega Potions
20 Times will get you 2: MP Spheres
50 Times will get you 3: Strength Spheres
100 Times will get you 3: HP Spheres
150 Times will get you 4: Mega Elixirs
200 Times will get you 1: Venus Sigil

Struck By Lightning
30 Times will get you 1: Ether
50 Times will get you 1: Elixir