D&D Monsters: White Dragons

While witches, evil sorcerers, and the like, may create freezing cold storms, beings that attack by virtue of simply being very cold are not common in myth, or indeed, in early fantasy literature. Tolkien mentions "cold drakes", but these are simply dragons that don't breathe fire, rather than being any supernaturally low temperature. Nonetheless, when Gygax was looking around for different attacks for the five basic chromatic dragons, intense cold seems (at least in retrospect) an obvious fit. Perhaps as a counterpoint to the fiery dragons being the most powerful these, the white dragons, became the weakest.

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1E

White dragons are not only the weakest of the chromatic dragons but the weakest of dragons overall. A step down from the black dragons, while they do have much thicker hides and stronger jaws, 1E white dragons have about the same ability to sustain physical injury as a tiger. In fact, their claws do less damage than a tiger's do, so it's possible that their legs are actually less muscular (or the claws are blunter, or smaller, which seems unlikely).

D&D Monsters: Red Dragons

Many medieval descriptions of dragons make no mention of them breathing fire, and this does not seem to be part of the original myths of the creatures. Nonetheless, the idea that dragons breathe flame does seem to have originated in medieval Europe, and is now de rigueur in fantasy depictions. It probably arose because of the association of evil dragons with hellfire, and the general idea of fire-breathing creatures certainly predates it (Leviathan breathes fire in The Book of Job, for example). 

In D&D, of course, it was originally decided that the five types of chromatic dragon should be distinguished by each having a unique attack, so that green dragons breathe poison, black dragons acid, and so on. Naturally, the most powerful of all the chromatic dragons was going to be the one that breathed fire, fitting the legends on which the broader idea is based.