100 years since the “Tri-State Tornado”: The deadliest twister in U.S. history that wiped out two towns

This week will mark the 100th anniversary of the deadliest tornado in U.S. history - a natural disaster that killed nearly 700 people across three states.

Known as the “Tri-State Tornado”, the twister tore a path of devastating destruction through parts of Missouri, Illinois and Indiana on Wednesday, March 18, 1925.

What to know about the Tri-State Tornado

After forming at about 1:00 p.m. in Ellington, Missouri, the Tri-State Tornado travelled a distance of nearly 220 miles, the U.S. National Weather Service explains.

Crossing over from Missouri into Illinois, it swept through the Prairie State and into Indiana, before finally dissipating in the southwest of the Hoosier State.

Over a period of around three and a half hours, the National Weather Service notes, the tornado killed 695 people, caused injuries to more than 2,000, and left thousands homeless.

Illinois was the hardest hit of the three states: of the overall death toll, it accounted for around 600.

Among the worst-affected individual communities was the town of Murphysboro, Illinois, which suffered 234 fatalities. A further 124 died in West Frankfort, Illinois.

You’ll find an interactive map of the Tri-State Tornado’s path on the National Weather Service’s website.

Where does the Tri-State rank among the world’s deadliest tornadoes?

Worldwide, the Tri-State Tornado is the second-deadliest on record.

The disaster’s fatality count is behind only 1989’s Daulatpur–Saturia tornado in Bangladesh, which is estimated by the World Meteorological Organization to have killed around 1,300 people.

What’s the definition of a tornado? Where’s the Tri-State on the Fujita Scale?

Described by the National Weather Service as “nature’s most violent storms”, tornadoes are defined by the agency as “a violently rotating column of air touching the ground, usually attached to the base of a thunderstorm”.

Tornado winds are generally known to be capable of top speeds of 300 mph, the National Weather Service says, while the American Meteorological Society adds that the diameter of a tornado can extend to distances of a little over a mile.

According to PBS, the Tri-State Tornado was about three-quarters of a mile in diameter - and had wind speeds so quick that they actually broke the 300 mph barrier.

Such characteristics mean it is little surprise to learn that the Tri-State Tornado holds “F5″ classification - the highest on the Enhanced Fujita Scale for measuring tornado intensity and area.

Speaking on a documentary aired by PBS in 2023, the meteorologist Kevin Deitsch also pointed out that tornadoes do not normally last anything like as long as the Tri-State Tornado.

“If you think of a typical tornado that we would see, [a duration of] one, five, maybe 10 minutes is the usual time frame,” Deitsch said.

“So for a tornado to be on the ground for over three and a half hours, it just shows the power that this tornado had.”

When and where are tornadoes most common in the U.S.?

According to the UCAR Center for Science Education, tornadoes are most typical in the spring and summer months, particularly May and June.

In the U.S., UCAR says, the weather phenomenon is most common in a part of the country known as the Great Plains - an area encompassing states such as Texas, Oklahoma, Kansas and Nebraska.

Just next to the Great Plains are Missouri, Illinois and Indiana, whose tornado count is lower than in the states mentioned above, per a National Weather Service tally, but is higher than many other parts of the U.S.

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