Extreme rainfall is wreaking havoc and growing worse with climate change
Dinah Voyles Pulver and Kevin Crowe • December 3 - 5, 2021
Over eight days of wild weather in June, the realities of a changing climate grabbed the nation by its shoulders and shook.
In Michigan, a deluge dropped 7 inches of rain in Detroit, swamping highways and stranding cars.
At least 136 dally rainfall records were set during storms across five states along the Mississippi River.
Tropical Storm Claudette soaked a swath of the South, flooding homes in Louisiana and in Alabama, where it dropped up to 8 inches of rain and claimed 14 lives.
Meanwhile, the drought-stricken West grappled with soaring temperatures that shattered century-old records, prompted heat warnings and ultimately killed more than 200 people.
Wlldfires exploded in Montana and scorched the earth in California.
Such events do occur naturally, but rarely have so many struck at once or to such an extreme degree, making it hard to ignore their connection to each other and to a warming world.
Rising temperatures and rising oceans have for years been framed as the impending disasters on the crest of climate change. But this year, like few before it, changing rainfall patterns bullied their way into the collective consciousness.
USA TODAY reporters analyzed more than a century of precipitation records from the National Oceanic and Atmospheric Administration and a unique collection of snow and rain extremes computed by Alaska-based climate researcher Brian Brettschneider.
Reporters read thousands of pages of climate assessments, scientific papers, weather reports and government documents. They interviewed more than 70 people, including climate scientists, academic researchers, local and federal officials, and residents forced from their homes by drought and flood.
Taken together, the reporting reveals a stunning shift in the way precipitation falls in America.
Heat has changed how moisture moves across the country. Scientists say it alters the flow of the jet stream, extends droughts and increases evaporation from land and from bodies of water, including the Atlantic and Pacific oceans, the Great Lakes and the Gulf of Mexico.
East of the Rockies, more rain is fallingand it's coming in more intense bursts. In the West, people are waiting longer to see any rain at all.
Readings from hundreds of rain gauges across the continental U.S. tracked for more than 100 years reveal a noticeable inflection point before the turn of the 21st century.
Of 285 weather stations, 44% get at least one more top rainfall event per year now than they did three decades ago, based on data compiled by Brettschneider. That means what used to count as the top three wettest rainfalls of the year now happen at least four times a year.
Nineteen places doubled their previous number of days of extreme precipitation - from three a year to six.
As deluges grow in frequency and severity, annual precipitation has increased for more than half the nation. At some point over the past three years, 27 states - all east of the Rocky Mountains - experienced their highest 30-year average since record keeping began in 1895, according to a USA TODAY analysis of NOAA data.
A dozen states, including Iowa, Ohio and Rhode Island, saw five of their 10 wettest years in history over the past two decades.
At the opposite extreme, eight states - including five in the West - had at least three record-dry years in the same time period. That's double what would be expected based on historical patterns.
As states rack up records for rainfall, flooding, droughts and wildfire, it's becoming clear our country was built for the climate of the past.
Roads, bridges, sewer systems and entire communities that decades ago seemed safefrom fire and flood now lie within one or both danger zones.
An October report by the nonprofit First Street Foundation warned that one-fourth of the nation's "critical infrastructure," including roads, utilities, airports and emergency services, now faces flood risk from rainfall sea level rise, as do 1 in 7 residential properties - about 12.4 million.
Heat, lack of humidity, and wind are combining more frequently to enhance the risk of wildfire. Climate Central, a nonprofit research organization, looked at 17 Western states and found parts of New Mexico now have at least 60 additional days when the fire risk is more extreme than 50 years ago.
Parts of 11 other states, including Arizona,California, Colorado, Oregon and Texas, saw more than a 100% increase in these "fire weather days."
These calamities displace families, claim lives and leave officials from coast to coast conflicted over which crisis to plan for next and how to pay for it all.
NOAA reported at least 133 "billion dollar disasters" in the decade ending in 2020, double the previous decade, at a cost of more than $867 billion. Meanwhile, the annual average number of flood claims paid by the Federal Emergency Management Agency also doubled between 1997 and 2020, to 52,000.
Scientists say it's too late to stave off some of the climate change-driven precipitation extremes we're experiencing today, But the nation could take steps to reduce greenhouse gas emmissions that amplify the weather extremes and take more aggressive measures to reduce flood rise.
Given the increasing frequency of weather disasters, "one would think the nation might be galvanized to action," said Rob Moore, a senior policy analyst with the Natural Resources Defense Council. "And yet we are not incorporating what we know about the future into our decisions about what we build, where we build and how we build as a nation."
What's causing It?
The earth has always produced erratic weather patterns. But now the heaviest downpours and droughts are growing more extreme. That trend started in the late 20th century, as the accumulation of greenhouse gases like carbon dioxide and methane reached critical levels in the atmosphere.
Climate scientists said these gases trap more of the energy radiating from the planet's surface, causing the earth to warm.
This warming doesn't just raise temperatures. It intensifies how water cycles between earth and sky.
Heat hastens evaporation. It draws more water into the air where it gathers into systems that can form wetter storms. For every 1.8 degrees Fahrenheit of warming, 7% more moisture is absorbed, said David Easterling, director of NOAA'S National Climate Assessment Technical Support Unit.
It's one of the reasons behind many of this summer's rainiest storms, including Hurricanes Henri and Ida, that flooded communities throughout the South and Northeast this August.
For these storms and others throughout the year, much of their moisture comes from the Gulf of Mexico, Great Lakes and Atlantic Ocean.
Gulf waters alone have warmed about 13 degrees over the past four decades.
A warmer Gulf contributes to more rainfall in hurricanes and tropical storms, but its moisture also helps form wetter storms as far north as Wisconsin, Easterling said.
At the same time, some scientists said rising temperatures have altered the summertime movement of the jet stream that transports moisture across the country. Weather systems that used to hustle along get stalled more often now, dumping more rain in one place.
Instead of flowing quickly across the north, the jet stream moves slower and gets bigger, wavy dips that trap high and low pressure systems in place, said Michael Mann, a climatologist at Penn State University and author of the book "The New Climate War."
The trapped highs and lows in the summertime affect the weather across the country, Mann said. For example, they can produce extreme heat, drought and wildfires in the West and drop huge amounts of rain to the east at the same time.
Scientists can't say for sure how much of the rain in each storm is directly attributed to the changing climate, Brettschneider said, but the shifts become apparent when comparing a sampling of current and older events.
More Intense rains
Climate change also has been blamed for fueling the intensity of the storms that unleashed record rainfall and sparked deadly flooding across Tennessee in August.
The day that storm hit started like just another rainy morning in Humphreys County.
Weather forecasters had issued flash flood advisories, warning of 2-4 inches of rain, but no one had predicted four times that much or the catastrophe it would bring.
Typical summer thunderstorms sweep through at 50-60 mph. But on Aug. 21, a system got caught up with a stalled front and traveled through at only 10-15 mph. Meeting up with a pool of Gulf moisture overhead, it forced storms to rain over the area again and again, dropping more than l2 inches of rain in seven hours in the small city of McEwen.
The total rainfall - 17 inches - broke the state's all-time record and triggered deadly flooding in Waverly.
Around 7 a.m., Joe Duncan looked outside and saw water rushing through his yard. He gathered his wife, daughter and two grandchildren and headed out through knee-high water to pick up his mother so they could evacuate. When they reached her house, Duncan turned around just in time to see his mobile home tilt sideways.
By this time, 9 inches of rain had fallen in six hours, sending Trace Creek out of its banks and raging toward Waverly in a muddy torrent.
Calls started lighting up the Humphreys County 911 Center.
The debris-filled Trace Creek hurtled toward a pair of bridges east of Waverly - one for U.S. 70 and one for the railroad. Mayor Buddy Frazier and others believe debris lodged at the bridges, creating a temporary dam until the water crashed through and sent a "tsunami" into Waverly.
Duncan's home slammed against a tree and split into three pieces. He said the nearby home built in the early 1900s also was destroyed.
Twenty people died in the disaster. They're among 144 flood-related deaths in the nation this year, the second-highest since 1985.
Rising temperatures also lengthen dry spells, creating wild swings between downpours and droughts.
The length of time between rain increased by three days on average across the West from 1976 to 2019, according to research published this year by scientists with the U.S. Department of Agriculture and the University of Arizona.
The researchers also found the longest interval between rains each year increased by 11 days in the West, to 32 days across the region. In the desert Southwest, it increased by 17 days to 48 days.
More dry days and drought
While increasingly intense rains fall east of the Rockies, the West experiences intense drought. Rising temperatures and lingering high pressure systems zap greater moisture from soils and plants.
"With precipitation you're only getting half of the picture," said Daniel Swain, a climate scientist at UCLA and the National Center for Atmospheric Research. "When it comes to drought, temperature is increasingly important, and temperatures are rising a lot."
Together, the intense heat and longer intervals between rains contribute to the conditions creating more recordbreaking wildfires in the West.
All but two of California's 20 largest wildfires have happened since 2003.
Oregon had one of its most destructive wildfire seasons on record last year with roughly 2,200 fires that burned more than 11 million acres and destroyed more than 4,000 homes.
One of those homes belonged to the Flores family in the Coleman Creek Estates mobile home park near Medford.
Seventeen years old at the time, Julio Bryan Flores woke up the morning of Sept. 8, 2020, looking forward to celebrating his mother's birthday when a neighbor's call alerted the family to danger, he said.
Soon ash fell from the sky. The entire neighborhood evacuated. Bryan's father, who had been away, returned home just in time to get the dog, but not his mechanics tools.
"We could see fires literally starting everywhere," Bryan said. "We were surrounded by them."
The family escaped, but the fire destroyed their home and possessions. When Bryan and his dad returned a week after the fire, "it was a nightmare."
"There were just the colors white and black everywhere, burned bicycles, destroyed cars, toys left on the street, just burned," Bryan said.
Once an intense wildfire burns through an area, it leaves the soil hardened and scarred and weakens its ability to absorb water. So when the rains come, they turn dry creek beds into raging rivers, like the one that swept up a Prius near Flagstaff, Arizona, in August and carried it down the street in a viral video.
The atmospheric river that swept across the West in late October dropped anywhere from 3 to 13 inches of rain across California, Oregon and Nevada.
Action needed now
Critical steps are needed - and soon - to try to keep downpours from growing evermore intense, correct past mistakes and adapt our surroundings to the new reality, experts said.
Many call for sweeping changes to curtail warming, upgrade stormwater and utility systems, and revamp federal guidelines and standards and stop building in vulnerable places.
"The future is still in our hands," Mann said.
Two things appear to be true for "pretty much everywhere that's populated and on land," Swain said. "Everyone is getting warmer and everyone is seeing, or should see shortly, more intense precipitation events."
Part of the problem is the nation's woefully outdated federal precipitation estimates and inadequate flood zone mapping, Moore said. Neither takes into account recent rainfall increases, much less future projections.
"We're still designing highways and stormwater systellls and siting people's homes without any consideration of what the weather is going to look like in 30, 40 or 50 years," Moore said.
Changing rainfall amounts and rising sea levels mean the estimates, such as a 1-in-100-year flood or a 1-in-25-year rainfall, aren't the same as they used to be. Neither set of estimates talces future projections into account.
The NOAA estimates guide governments, engineers and others when designing infrastructure. A new generation of estimates, called Atlas 14, began in 2002 but has never been completed for the entire country.
One study showed that for Michigan, Wisconsin, Iowa and Minnesota, the historic estimate of a 1-in-100-year storm is now a 1-in-40-year storm, said Daniel Wright, an assistant professor of civil and environmental engineering at the University of Wisconsin-Madison. "These sorts of storms are happening 2 1/2 times as often as they should be."
Labeling storms as once-in-a-generation gives people the false impression they can't have another, said Peter Schultz, vice president of climate adaptation and resilience for ICF, an international climate change consulting firm.
"If you have dice and you roll a three, that doesn't mean the next time you roll the dice you can't get a three, you absolutely can," he said. "Nature is still rolling the dice, but it's not fair dice anymore, it's dice that are coming out toward those higher numbers."
Warming planet to blame for heavier rains
Nicole Carroll • Editor-in-chief • USA TODAY
Think your area has had more rain than usual? You're probably right.
Think your area has had less rain than usual? Again, you're probably right.
For our climate change investigation out this week, called Downpour, USA TODAY reporters used 126 years of monthly data from the National Oceanic and Atmospheric Administration to analyze average annual precipitation at 344 climate divisions. They used daily precipitation data from weather stations to measure the change in frequency of extreme rain events across the U.S. from 1951-2020.
"We were hearing a lot about extreme rainfall, stories of flooding, people with sewer backups, people flooded out of their homes, and we wanted to know, is this happening everywhere?," said Dinah Pulver, one of the project's lead reporters. "How many people, how many places, are contending with this kind of rainfall?
We found more than half of the nation's 344 climate divisions had their wettest periods on record since 2018. We calculated the same rolling averages for states.
"East of the Rockies, more rain is falling, and it's coming in more intense bursts," our report finds. "In the West, people are waiting longer to see any rain at all.
"Taken together, the reporting reveals a stunning shift in the way precipitation falls in America."
Specifically, our reporting finds:
• At some point over the past three years, 27 states - all east of the Rocky Mountains - hit their highest 30-year precipitation average since record keeping began in 1895.
• A dozen states, including Iowa, Ohio and Rhode Island, saw five of their 10 wettest years in history over the past two decades.
• Michigan saw six of its wettest 10 years on record over the past l3 years.
• In June, at least l36 daily rainfall records were set during storms across five states along the Mississippi River.
• At the opposite extreme, eight states - including five in the West - had at least three record-dry years in the same time period. That's double what would be expected based on historical patterns,
"People talk about the climate we're leavlng for our kids or the climate of the future," Pulver said. "But the realty Is limate change is here now and It's affectlng most of us."
So how does the warming planet impact rainfall?
Michael Mann, a climatologist at Penn State University, told our reporters the greenhouse effect is important to keep Earth from freezing, but excess heat greatly reduces the temperature difference between the warmer tropics and cooler polar regions in the summer.
Mann said that reduction in the temperature difference slows down the jet stream, which makes it weaker and wavier in the summer. That means weather systems moving across the country can slow or stall more often.
"The gentle rains for a number of days are kind of disappearing and are being replaced by downpours," said Chris Davis, USA TODAY's executive editor for lnvestigations. "And that in and of itself has a lot ramifications, everything from flooding, to mudslides out west, to how much fertilizer gets picked up and carried into the Mississippi River and down into the Gulf of Mexico."
In the West, the high temperatures and lingering high pressure systems pull moisture from soil and plants. The increased heat and long periods between rains contribute to record wildfires.
"They're all interconnected to the impact that climate change is having on these persistent weather extremes," Mann said. "It's not a contradiction to have huge floods, unprecedented floods and unprecedented heat waves and droughts at the same time."
The downpours bring a deluge of problems. Stonnwater, sewage and drinking water pipes are 50to100 years old and nearing the end of their life expectancy, said Christine Kirchhoff, an associate professor in Civil and environmental engineering at the University of Connecticut.
That leaves communities increasingly vulnerable to flooding. It also prompts massive releases of treated and untreated wastewater into waterways, which can cause or lntlame gastrointestinal issues.
Downpours also push fertilizer from Midwestern fields into rivers, which ultimately poison the Gulf of Mexico.
"But it's not just the Gulf of Mexico," reported Ignacio Calderon, with our partner the Midwest Center for Investigative Reporting. "Fertilizer runoff wreaks havoc on rivers and lakes across the country. It contaminates drinking water, harms aquatic life and sickens both people and pets."
It took our reporter months to collect, organize, analyze and publish this information. Now, you can see how rainfall has changed In your community in just seconds.
At downpour.usatoday.com, you can enter your address or ZIP code to see how rainfall has changed dating back to 1895.
Data reporter Kevin Crowe led our data analysis efforts, a huge undertaking given the number of climate divisions and years of data. Crowe ran our methodology by several scientists to make sure our findings were spot on. We also drew on the data and expertise of climatologist Brian Brettschneider.
What stood out?
"Looking at states in the Midwest and in the Northeast and just how much more rain places like Michigan, Indiana or Ohio or Pennsylvania are getting, that kind of boggled my mind," Crowe said. "I mean the Great Lakes are higher, all sorts of things kind of indicate that there's more water falling, but just seeing the overall trend lines was still pretty surprising."
Our team also dreamed up creative ways to help our readers understand the changing rainfall. Developer Chris Amico wondered if we could create a soniftcation of the hundred-plus years of rainfall data.
Pulver took that challenge to Florida's Full Sail University, where musicians composed songs based on changing precipitation patterns in several states.
Timothy Stulman, a composer and department chair of music composition, took on Pennsylvania. He gathered sounds of wind, thunder and rain, then combined those with flute and cello melodies. The density and volume directly correlate to the data.
"If there was a really high rainfall year, I would choose recordings of intense rainfall, strong winds, and mix them with loud thunderclaps," he told us. "So it's not a single recording of a storm, but rather various storm elements blended together based on the rainfall data."
The point of all of this work is to help people understand the impact of climate change, right now, in their specific communities.
"These extreme events are not coincidence. They're really all part of the same pattern," said investigative editor Emlly Le Coz.
"You still hear terms like '100-year rainfall event' or this is a 'SO-year flood.' Those terms are sort of meaningless now. What's the point of calling it a 100- year event if it's happened five times in the last decade?
"There's a lot that we need to do to wrap our brains around the new reality that we're living in."
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