One should never underestimate the power of an average. Cunning things they are, and patient, sometimes lurking for months or years, dawdling in the wings, before striding out to assert themselves and even the score.
Our rainfall this year, for example. At the end of October we were four inches below the figure for the first ten months of the past five years. So it tipped in November, with five inches of rain, setting December the easy task of making up the precise annual average figure. Q.E.D.