Weather Talk: Above and below average are not balanced
It seems the weather gets cold for a while and then warms up again, or it snows a lot and there is a flood before the weather goes dry. Back, forth, up, down; weather is always changing from one side of average to the other.
This can happen on a timescale of a few days, but it can also happen on a timescale of weeks, months, years or even longer.
There is a general misconception that these ups and downs balance out over time, but they do not. Long-term weather records show that weather is distinctly nonlinear. Over short and long periods of time, such as days and weeks or decades and centuries, the warm spells do not completely balance out the cool spells. Likewise, wet weather is not balanced by drought.
This means that our concept of "average" is of limited usefulness.