Water exists in three states: liquid, damp and solid. The gaseous state (or water vapor) is reached when temperature is more than 100°C. The solid state, or ice,  is reached when temperature drops below 0°C. Ice may form directly via the gaseous state which is called "sublimation". But, more common, it may also form directly via the liquid phase which is called "freezing".

The picture of some large ice plates covered by snow on this canal was taken after a ten day period of subzero temperatures, which even dropped as low as -13°C.