What Is Average?

Halfway through April and it is looking like another colder than average month.  December, January, February, and March have all been significantly colder than average.  April will likely make five months in a row.  Last October and November were also colder than average but only by an insignificant fraction of a degree. September was warmer than average but the summer months last year were only slightly warmer than average.  Average is only the average of the past.  There is no rule that weather has to conform to averages either by remaining near average or by swinging equally one way and then the other.  In this sense, our weather is non-linear, which means it does not converge to an average over time.  We present weather averages only as a way to roughly compare.  For most weather records, what we call, “average” is only the average of the past three full decades.  So what constitutes average weather actually changes over time as our climate goes through changes.      Meteorologist John Wheeler

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