Weather.com - 9/14/13, Jon Erdman
A collection of ingredients came together to produce a destructive, deadly flash flood event in northern Colorado, including Boulder and parts of the Denver metro areas in mid-September, 2013
From the afternoon of September 9 through midday on September 13, 14.62 inches of rain had fallen in Boulder, Colo. This included an incredible 9.08 inches of rain on September 12, alone!
According to the Western Regional Climate Center, the previous all-time record rainfall for any calendar day in Boulder was a 4.80 inch deluge on July 31, 1919., in records dating to 1893. September 12th's total almost doubled the previous record wet day.
