Heavy rainfall events more common nationwide


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This map illustrates the percent increase in heaviest precipitation events from 1958 through 2016. (Climate Central)

Jenna Ladd | May 11, 2018

As the climate continues to warm, many U.S. cities are experiencing heavy rainfall more frequently.

Research and news organization, Climate Central, examined the number of days per calendar year that each of 244 sites nationwide experienced 0.25, 0.50, 1, and 2 inches of precipitation from 1950 through 2017. The report found that incidents of heavy rain events are increasing in frequency in all regions of the U.S. In Des Moines, the number of days per year where the city experienced two or more inches of precipitation has increased by about seven percent since 1950.

For each 1°F of global warming, Earth’s atmosphere becomes four percent more saturated with water. This makes more moisture available to condense and fall down as precipitation. As a result, extreme floods are more likely to happen now than they were in the past. According to NOAA, 29 flood disasters that cost more than $1 billion each have happened since 1980. In Iowa alone, floods have caused more than $18 billion in damages in the last thirty years. That puts us in fourth place nationwide for the number of floods experienced since 1988.

The northeastern United States has seen a 55 percent increase in heavy precipitation events from 1958 through 2016, the sharpest increase in the nation, according to the report. The midwest follows close behind, with a 42 percent increase in heavy precipitation events.

Users can determine whether incidents of heavy rainfall have increased in Dubuque, Mason City, Ottumwa, Sioux City, and Waterloo by using Climate Central’s interactive map.