Anyone who has read the Harry Potter books and/or have seen the films must notice the lack of safety in the wizarding world. From the forbidden forest and deadly creatures at Hogwarts to Quidditch, wizards and witches seem to care little about safety.
That includes going into the water in cold weather. A good example is in The Goblet of Fire, when the Tri-Wizard champions have to compete in the black lake and each save one individual. However, they do it in February, where the weather freezes.
Although the novel doesn’t specify the champions’ outfits (except Harry’s, which were his school robes), in the movie, they wore summer attire, while everyone else wore winter gear. Fleur wore just a bathing suit, while the boys had shorts and tank tops. How were they not cold?
You’d think they would have worn long-sleeved wet suits, or something to get the champions warmer. Yet, they turn out okay. They also don’t suffer any effects of Hypothermia – which can go as far as affecting brains.
Do charms that prevent hypothermia exist in the Harry Potter universe? If so, does the black lake at Hogwarts have them?
Even if the answer to both questions is yes, there couldn’t have been any in that pond Harry jumped into in The Deathly Hallows, without his clothes on. After he leaped into the water, he didn’t seem to suffer one bit.
Lots of people point out that if there is a potion to regrow bones, there should be a spell or something to fix Harry’s eyesight. That way, he wouldn’t need glasses.
But Harry is not the only wizard to wear glasses. Dumbledore, McGonagall, and Myrtle wear them, too. So, I assume that magic can’t repair eyesight – although it can fix glasses – at least in the movies.
So, could magic keep magicians from freezing and experiencing hypothermia? It seems to me that they do. But, of course, only J.K. Rowling could either confirm or debunk any theories about the Harry Potter universe.