The August derecho was the costliest thunderstorm ever to strike the United States. The $7.5 billion amount attached to the event is just one of the facts shared about the derecho in the upcoming book “Derecho 911: Iowa’s Inland Hurricane” by husband and wife team Terry Swails and Carolyn Wettstone.

The authors also extensively highlight Marshalltown throughout the 170-page book, available for purchase on Tuesday.

“We consider Marshalltown to be the epicenter of the storm,” Swails said. “In Marshalltown is where the storm took off and people really became aware of the event. That is where it became a superstorm. It is the place where it became the derecho.”

Technically, Swails said the storm began west of Ames, but when it picked up speed, the derecho was the equivalent of the F2 tornado covering a 40-mile-wide, and 150-mile-long range.

“That is flat-out unheard of and rather remarkable,” Swails said.

Weather and storms are something Swails carries a vast amount of experience and knowledge. He spent 43 years working in television broadcast, including as the chief meterologist for KGAN in Cedar Rapids, where he won a Midwest Emmy for his coverage of the Iowa City tornado.

He also calls himself a historian of Iowa weather.

In fact, the term “derecho” was first used by Gustavus Detleft Hinrichs of Davenport in the 1800s. The word is Spanish-based and means “straight-line wind storm.”

“The derecho was the largest natural disaster in the state’s history,” Swails said.

Derechos are not uncommon in Iowa, he said. There might be one or two per year, but none that reached the August 100 to 140 mph winds which lasted more than 30 minutes.

“Typically, these storms show up in Iowa and . . . bam . . . they’re over with,” Swails said. “This was very unusual.”

He does not believe the chances of another derecho of this magnitude are very high. Perhaps, Swails said in another 30 years, but he had never seen anything like it.

Due to the expansive area the derecho covered and the large amount of damage inflicted, Wettstone and Swails wanted to not only include plenty of images in the book, but science to give people a better understanding of derechos.

“This is a difficult severe weather event to predict,” he said. “It is a lot harder than tornadoes and hurricanes. We want to give people a better understanding of the meteorology and the science.”

“We wanted to create something historically accurate that would stand the test of time so if people want to know more about derechos, they can read it and walk away with a better understanding,” Wettstone said.

Swails and Wettstone already have 800 presales of the book, and they are personally signing them to send to the buyers by Dec. 17. They would make great Christmas gifts, Swails said.

The couple want to wait until after the COVID-19 pandemic calms down before going on any book tours. So, they are tentatively planning for something in the spring of 2021.

One impact they hope will come from the book is pushing the need for better severe thunderstorm emergency alerts. Swails said he hopes something will be available next year.

“Now, you get an alert on your phone about a storm, but this alert should let people know when the storm is bad enough to where they need to get to a basement.”

Contact Lana Bradstream at lbradstream@timesrepublican.com.