Thunder was most famous for his ability to alter the weather, though many experts believe that this was only a minor power compared to the manipulation of sound-waves: it has been said that Thunder could hear people whispering from over ten miles away. Linguistics expert Doctor Rhonda Heathers recently announced that, judging by his accent, Thunder almost certainly spent his formative years in Estonia (however, given his unparalleled skill at controlling sound-waves, it's possible that his accent was an affectation designed to further disguise his identity).
Though his real identity has never been made public, it was once rumoured that he was Oliver Jason Barr, a professional body-builder from Montreal. Barr's frequent public denial of the rumours made little difference: he looked like Thunder, and had the same height and build (6'5" / 195.5cm). The rumours faded when it was later discovered that they had originated from Barr's manager in a successful attempt to boost his client's ratings.
Costume:
Thunder always wore a distinctive skin-tight costume of dark-green and dark-grey material.