Pure water doesn't freeze at 32F ?? This has me curious. I am reading a Scientific American article, which the following is from(emphasis mine): In flight icing is where the airplane is flying through clouds made up of small liquid water droplets. These liquid water droplets can be sustained as liquid below the freezing point. Everybody knows that 32 degrees Fahrenheit (0 degree Celsius) is where water freezes. It turns out that if the water is very pure—if it is condensed out of the atmosphere—and there is nothing for that water to freeze on, it can be sustained below the normal freezing point. What we find in the wintertime is clouds that are made up of small water droplets where the water temperature can be as low as negative 40 degrees C. Here comes this plane flying through the cloud, and the water droplets impact the airplane and then freeze because now they have a surface to freeze on. Source: http://www.scientificamerican.com/article.cfm?id=ice-flight-3407 Anyway, I'm confused. Can water remain liquid at -40 C. ?