Oh, don't get me wrong. I'm sure the source material was Thunder, and none of you made any mistakes about that. I was bitching about the "missing localization" that is simply ubiquitous when it comes to Japanese material, especially in JRPGs (what the fuck is "Thunder Magic" or "Thunder Resistance"? That's not how that works in English) .
That being said, I am willing to drop my argument in this particular context, because it does seem like the words used in the original text reference something, rather than be "normal spoken language", which makes it perfectly okay to just ignore and freely localize (i.e: if Japs have "thunder gods", localizing them to "Lightning Gods" isn't necessarily the right move here, I can agree with that.)
The only problem I have with that, is that it is 100% lost in translation. Look at this picture, for an instance.
Thunder Magic? I'm sure that too has a reference to Japanese Myth, but what the hell is Thunder Magic in English? Why are there no footnotes to give it more context? Because it looks stupid as all hell otherwise.
....Furthermore
雷 (kaminari/ikazuchi/rai) means thunder/lightning bolt.
This is pretty much why "Thunder" is a pet-peeve of mine at this point. Even if T and L are totally synonymous in Japanese, making out sentences which say "Thunder" instead of "Lightning" make no sense to me. It's synonymous in Japanese, not in English.