Climatology is the science of climate, which in turn is the composite of all weather events. It should be noted at the outset that climate fluctuates on all time scales: monthly, yearly, decadally, centennially, and millennially. Thus, climate is a statistical collective. It has often been described in terms of mean values of particular climatic elements, but it encompasses a wide range of values, including occasional extremes. Although atmospheric conditions and variations follow well-known physical laws, the day-to-day variations and those for longer intervals can, for many purposes, be treated like quasirandom variables. They can be represented by statistical distributions applicable to stochastic universes.