Hi, As the title said, I had 3 glasses store water in my room near the window. I drank 1 and a half of 3 glasses water and go to sleep. But after about 4 or 5 hours when i still sleep i hear some loud sound and woke up, I saw 1 empty glass broke in half and 1 still had some water broke. The water inside those glasses is cool tape water and the room temperature at that time is about 20 degrees ( cause it was around 2am). I know that many people asked this question but I think that my case is different from them cause I always use cool water and never bring those glasses near the sun light. Sorry if my English is too bad cause English is not my mother language.