Water boils at hundred degrees. It is the first basic point of Celsius temperature scale. However at what temperature should water boil? You see the temperatures of boiling of various substances depend on a situation of elements, included in structure of their molecules, in Mendeleev periodic table. The less the ordinal number of an element is, the less its nuclear weight is- the less the temperature of boiling of his its combinations is. Defining temperature of boiling of water as of hydride oxygen according to the situation of oxygen in the Periodic table, we will see, that water should boil at eighty degrees below zero. It is possible to imagine, what would happen, if our water boiled at such temperature. The oceans would begin to boil, there would remain no water on the Earth, and there would never appear any cloud in the sky.