Harvey marks the most extreme rain event in U.S. history

The rain from Harvey is in a class of its own. The storm has unloaded over 50 inches of rain east of Houston, the greatest amount ever recorded in the Lower 48 states from a single storm. And it’s still raining.

John Nielsen-Gammon, Texas state climatologist, said a rain gauge in Mont Belvieu, about 40 miles east of Houston, had registered 50.4 inches of rain through midday Tuesday. This total exceeds the previous record of 48 inches set during tropical cyclone Amelia in Medina, Texas in 1978.

All rainfalls totals from this storm are still preliminary and require review. But, if verified, this amount breaks not only the Texas state rainfall record but also the record for the remaining Lower 48 states.

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“The 3-to-4 day rainfall totals of greater than 40 inches (possible 50 inches in locations surrounding Santa Fe and Dickinson) are simply mind-blowing that has lead to the largest flood in Houston-Galveston history,” the National Weather Service office serving Houston wrote.

From the perspective of the amount of volume unloaded in the United States from a single storm, Harvey has no rival.

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The Space Science and Engineering Center at the University of Wisconsin at Madison determined that many areas of Southeast Texas have received rain that is expected to come around only once every 1,000 years (or having a 0.1 percent probability of occurrence), assuming a stationary climate.

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