Obviously yearly rainfall totals give us a better idea of the degree of drought, but how much variance is typical in yearly rainfall totals? What is the standard deviation on annual rainfall amounts at RDU?

MIKE MOSS SAYS:        Matt,    Using data from the current "climate normals" period of 1971-2000 at RDU, the average yearly precipitation there is 43.1 inches, and the standard deviation about that mean is +/- 6.4 inches. So, historically we have seen between 36.7 and 49.5 inches about 67% of the time, and should fall between 30.3 and 55.9 inches about 95% of the time.