Approximately 74 percent of our average annual precipitation falls during just six months: May through October. Based on the current complete three decades, the month with the highest average rainfall by far is June with 3.90 inches. May and July are a distant second and third at 2.81 inches and 2.79 inches, respectively.
September is the fourth rainiest at 2.57 inches followed closely by August at 2.56 inches. October is the other relatively rainy month with an average of 2.15 inches.
September and October may seem wetter than the other warm weather months because evaporation rates are much lower in the fall. The lower evaporation rates are a result of cooler temperatures, shorter day length and a lower sun angle. This causes the ground to remain muddy longer after a fall rain than during the spring or summer months.