There is an interesting story in the Washington Post, What the Harvey deluge would look like where you live, that includes a tool that shows how much flooding would be predicted to occur if the 51.88 inches of rain (which fell on Houston) were to fall where you are. It is easier for us to understand things when they are more directly related to our own situation.
I used the tool for Indianola, Iowa, where I am currently living, and found the predicted water levels would be around 8 feet!
The article references Mapzen for help creating this tool.
Although that amount of rainfall is unlikely for Iowa, precipitation patterns are changing. We are already experiencing a statistically significant increase in heavy rainfall events.
The following figure shows trends in significant heavy rainfall events from the article Changing Frequency of Heavy Rainfall over the Central United States from the American Meteorological Society.
“By focusing on the stations without changepoints, we found that 93 of them showed statistically significant trends, the vast majority of which were increasing (90 vs 3). Stations with increasing trends tend to be located in the northern part of the domain, in particular over Missouri, Illinois, Iowa, Minnesota, and Wisconsin.”