Heavy Rain & Flooding

More heavy rain is one of the hallmark signs of climate change. As the atmosphere warms, more water evaporates from soils, plants, lakes, and oceans. For every additional 1°F of warming, the atmosphere is capable of holding an additional 4 percent of water vapor. So when this additional water vapor condenses into precipitation, it leads to heavier rain — or when cold enough, heavier snow. The amount of precipitation falling in the heaviest one percent of all events is increasing across the U.S. — up 55 percent in the Northeast and 42 percent in the Midwest since 1958.

While there are other human factors associated with flooding, such as engineering of waterways and land development, the fact is that more downpours increase the risk of flooding. This expands the risk zone into areas that were previously safe from floods. Also, heavier rain increases erosion and runoff, removing agricultural topsoils and increasing the flow of pollutants into our waterways.

Resources for covering heavy rain and flooding:

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Interactives

Across U.S., Heaviest Downpours On The Rise

Very heavy downpours are happening more often. Watch how many more of the rainiest days on record are happening now compared to the past.

Explore on Climate Central

Reports

Hurricane Harvey Rain Attribution Analysis

Heavy rain with Harvey was three times more likely and 15 percent heavier as a result of climate change.

Read the WWA report

When it Rains it Pours, and Sewage Hits the Fan

Increasing heavy downpours, fueled by climate change, cause billions of gallons of sewage overflows nationwide.

Read the Climate Central report

Louisiana Deluge Attribution Analysis

Heavy rain in 2016 Louisiana deluge was 40 percent more likely and 10 percent heavier as a result of climate change.

Learn more on WWA

Across U.S., Heaviest Downpours On The Rise

Across most of the country, the heaviest downpours are happening more frequently, delivering a deluge in place of what would have been routine heavy rain.

Read full report