Corrected entry: When the Dementors are boarding the train, everything starts to go cold, so much so that the water on the windows starts to freeze, and even more noticeably the water in the bottle completely freezes. Once the Dementors have gone, the windows are completely free from ice and the water in the bottle has melted again. This is not possible in the short space of time that passed.
Sereenie
1st Oct 2006
Correction: Neither water nor windows can freeze that fast either. Dementors are magic creatures, and have magical effects on their surroundings.
Sereenie