The rain started falling in Colorado on Wednesday, September 11th. It rained, and rained, and continued to rain over the next several days. The rain on the 12th was particularly heavy when 4 to 6 inches of rain fell in less than a 12 hour period. In some places over 15 inches of rain fell during the multi-day storm. The creeks and streams rose and rivers overflowed their banks. According to the Colorado Division of Water Resources, water in many of the rivers and creeks had flows of over 1,000% than normal levels at the height of the flooding.