Alex Epstein, author of "The Moral Case for Fossil Fuels," blamed failures on the state's embrace of wind and solar energy.
More than 7 inches of rain caused flooding in Nashville over the weekend.
The city of almost 700,000 remained under a flash flood warning Sunday morning.
More severe weather was forecast through Sunday in parts of the region.
Newnan, southwest of Atlanta, was damaged by an overnight tornado that struck its downtown. One person in Coweta County died from a medical emergency.
One person was killed during Friday's storm in Coweta County, Georgia. Alabama authorities previously said 5 people were killed in that state.
Health officials are continuing to investigate the causes of deaths that may be related to the winter storm disaster that paralyzed the state in February.
Strong and long-lived tornadoes, hail the size of baseballs or larger and damaging winds in excess of 75 mph are all possible Thursday across the South.
The National Weather Service has turbocharged its lagging forecast model to better predict extreme weather events such as hurricanes, blizzards and downpours.
"We were hoping it will only be a 1-in-20-year event. Now it looks like a 1-in-50-year event," New South Wales Premier Gladys Berejiklian said Sunday.
With nearly two-thirds of the United States abnormally dry or worse, the government’s spring forecast offers little hope for relief.
In North Carolina, TV anchors fled a studio as a circulating storm passed overhead. The weather comes after tornadoes in Mississippi and Alabama.
Multiple tornadoes occurred with some damage to homes and businesses, forecasters in Alabama said. Warnings covered that state and others Wednesday evening.
“This is the most intense sandstorm in China in the past 10 years," China's National Meteorological Center said Monday.
With snow moving through the region, nearly 2,000 weekend flights at Denver International Airport have been canceled.