58 Feet of Rain in One Year

In January, we unveiled five of the most incredible snowfall extremes ever recorded in the United States. But after May 2015 marked the wettest month on record for the Lower 48, we are shifting gears and looking at some of the all-time rainfall records for the country.

On the following pages, you will find the six most incredible U.S. rainfall records that we selected from a list compiled by NOAA. We begin with one location that holds the records for the most rain in a single month and a year.

Located in Hawaii on the island of Maui is the Puu Kukui rain gauge. The rain gauge is in the West Maui Mountains at an elevation of 5,771 feet.

In March of 1942, Puu Kukui recorded nearly 9 feet (101 inches) of rainfall, which stands as the greatest precipitation total ever recorded in one month in the United States. Puu Kukui also holds the annual rainfall record for the United States with more than 58 feet (704.83 inches) of rain in 1982.

According to the United States Geological Survey, rainfall amounts in the mountains are enhanced by fog drip at higher elevations where the montane forest canopy intercepts cloud water.

Average annual rainfall quickly tapers off from 370 inches at Puu Kukui to less than 30 inches near the lower elevations at the coast, which reinforces that elevation plays a huge role in enhancing rainfall at this site.

Next, we head back to the mainland where the greatest 24-hour rainfall total was observed more than 30 years ago.

Claudette Dumps 40+ Inches in Alvin

Slow-moving tropical systems have a reputation for dumping enormous amounts of rainfall in a short period of time.

In late-July of 1979, the center of Tropical Storm Claudette moved slowly inland near the Texas/Louisiana border. Torrential rainfall fell along the southeast Texas coast, including the Houston metro area.

The heaviest amount was recorded just to the south of Houston in the town of Alvin. An observer measured a record 43 inches of rainfall in just 24 hours, which stands as the greatest 24-hour rainfall total in United States history. The storm total beyond the 24-hour record was 45 inches.

We head to our farthest north location on this list of rainfall extremes for the biggest 12-hour rain amount.

Three Feet of Rain in 12 Hours

In northwest Pennsylvania, the town of Smethport recorded nearly three feet of rain (34.30 inches) in just 12 hours on July 18, 1942. This is the biggest 12-hour rainfall total in United States history.

Breaking it down a little more, an amazing 28.50 inches of this total was estimated to have fallen in just three hours! This is the record greatest three-hour rainfall total in U.S. history.

According to Extreme Weather by Christopher Burt of Weather Underground, hillsides in the area were stripped of vegetation to the bedrock. A total of 11 people were killed by the flooding rains.

Next, we look at the most incredible one-hour rainfall amount.

More Than a Foot of Rain in an Hour

If you think an inch or two of rainfall in a single hour is impressive, you'll be amazed by what happened almost 70 years ago in central West Virginia.

A rainfall total of 13.80 inches was estimated to have fallen near Burnsville over the course of just one hour on August 4, 1943.

A 1952 report from the United States Geological Survey on the flooding rains stated that many small streams and a stretch of the Little Kanawha River near Burnsville and Gilmer reached their highest levels known.  A total of 23 people were killed by the floods and numerous homes were swept away. Damage estimates at the time were around $1.3 million.

For the ultimate one-minute deluge we head east to the state of Maryland.

All-Time One-Minute Rainfall Record

In just 60 seconds, 1.23 inches of rain fell in Unionville, Md. on July 4, 1956. If that rainfall rate had continued for an entire hour - it did not - the total would have been 73.80 inches!

Not only is this a record United States one-minute rainfall total, it's also the world record.

How could a rainfall rate of this intensity occur? Our Severe Weather Expert Dr. Greg Forbes explains in this excerpt below from a 2010 blog entry:

It seems likely that it would require a thunderstorm occurring in a very moist, warm environment. The moist, above-freezing layer should extend very high so that there would be a deep layer of accumulating rain rather than a lot of hail. The thunderstorm would need to have a strong updraft to accumulate a lot of rain suspended aloft as shown in the first image at the right.

Then, somehow, the updraft should stop and be replaced by a strong downdraft that would drive the rain toward the ground much faster than it would fall naturally, as shown in the second image at the right. That combination is the only one that seems likely to make it rain at such extreme rates.

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