Tri-State tornado: 100 years since the deadliest twister in US history

March 2025 marks the 100 year anniversary of the deadliest tornado in US history.

The storm killed 695 people, completely levelling towns in its path.

It hit on 18 March 1925 leaving a trail of destruction across the states of Missouri, Illinois and Indiana and became known as the 'Tri-State' tornado.

In addition to the reported fatalities, more than 2,000 people were injured.

Tornado speeds are estimated from the damage they leave behind. It's thought that the Tri-State tornado reached the top rated F5 strength on the original Fujita scale.

On this scale, according to NOAA (National Oceanic and Atmospheric Administration), wind speeds would have reached between 261-318mph (420-512km/h).

These winds would have been powerful enough to lift some houses off of their foundations and carry them considerable distances.

The tornado was a mile-wide at times, and had an average forward speed of 62mph (99km/h) - exceptionally rapid for a twister. Even if you could have seen the violent storm approach, there would have been no way to out-run it. Communities including Biehle, Missouri; Gorham, Illinois; and Griffin, Indiana were completely destroyed.

Most witnesses didn't report seeing a classic tornado funnel, which suggests it is quite likely that this was a 'wedge' tornado. A wedge tornado is an informal term for a tornado that looks wider than the height measured between the cloud base and the ground.

The storm caused $16.5m (£12.74m) of damage in 1925; accounting for inflation that would be about $3bn (£2.3bn) in today's money.

There is some debate about the length of the storm's swathe of destruction. It is possible that the funnel may have lifted off the ground for short periods and/or that there may have been multiple tornadoes at times. However, the track of damage stretched at least 219miles (352km), with the tornado lasting three and a half hours.

The advent of accurate forecasts and warnings means we probably won't ever see a repeat of the large loss of life, as that caused by the Tri-state tornado. But even with modern technology, tornadoes still bring devastation and can be fatal. However the 2011Joplin tornado was considered a rare weather event, killing over 100 people, making it the deadliest tornado since 1947.