Spectacular photographs show the moment Niagara Falls FROZE
Niagara Falls fact. It's true, there have been winters so cold in Canada that Niagara Falls froze. You can see pictures in the historic Brock Hotel in Niagara Falls (along with a picture of Marilyn Monroe visiting the Falls!!)
I must disagree on the "fact" about the dementors. On page 14, chapter one of Harry Potter and the Order of the Phoenix, Fudge states "That's right. And they're [the dementors] breeding. That's what's causing all the mist."