The widest tornado ever recorded was the El Reno tornado in Oklahoma on May 31, 2013, which reached about 2.6 miles wide. The longest-lasting and farthest-traveling record-holder is the Tri-State tornado of March 18, 1925, which tracked about 219 miles across Missouri, Illinois, and Indiana.

What “biggest” can mean

“Biggest” isn’t a single fixed record for tornadoes, because people usually mean one of three things:

  • Widest tornado: El Reno, 2013.
  • Longest path / most extreme track : Tri-State tornado, 1925.
  • Most damaging or deadliest : that depends on casualties and context, not size alone.

Most likely answer

If you mean physically largest by width , the answer is El Reno. It was documented as the widest tornado ever recorded, and reports describe its peak width at about 2.6 miles (4.2 km).

A useful distinction

A tornado can be huge without being the deadliest, and a deadly tornado can be relatively narrow. In other words, size, strength, and destruction do not always line up the same way.

TL;DR

  • Biggest by width: El Reno tornado, 2013
  • Biggest by path length / “most extreme”: Tri-State tornado, 1925

What usually gets people’s attention is width, so that’s why El Reno is the standard answer.