Last updated November 19, 2021

New Orleans Flood August 2017

United States

A very small, slow-moving storm pinpointed parts of New Orleans, Louisiana on August 5, dropping heavy rainfall that overwhelmed city pumps and helped to drive heavy flooding. Some neighborhoods witnessed as much as 8 inches of rainfall in the span of three hours[1], an extreme micro-burst expected to occur roughly every hundred years on average according to NOAA rainfall frequency tables and New Orleans city officials.[2][3]

Just two weeks prior the same areas endured extreme rainfall that mounted to as much as 4.5 inches in less than hour[4], a burst expected to occur roughly every fifty years[2]. New Orleans has seen a 62 percent increase in the number of heavy downpours since the 1950s.[5]

Increasing extreme rainfall is one of the clearest observed signals of climate change, and the fingerprint of global warming has been firmly identified in the global trend of increasing extreme precipitation. Back-to-back years of extreme August rainfall events are consistent with the global trend of increasingly frequent extreme and record-breaking rainfall events.

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Dumaine and N. Derbigny Streets under water after a torrential downpour flooded city streets on Saturday, August 5, 2017. Photo: Michael DeMocker, | The Times-Picayune