This article lists various tornado records. The most "extreme" tornado in recorded history was the Tri-State Tornado, which spread through parts of Missouri, Illinois, and Indiana on March 18, 1925. It is considered an F5, even though tornadoes were not ranked on any scale at the time. It holds records for longest path length at 219 miles (352km), longest duration at about 3½ hours, and fastest forward speed for a significant tornado at 73mph (117km/h) anywhere on Earth. In addition, it is the deadliest single tornado in United States history with 695 fatalities.[1] It was also the third-costliest tornado in history at the time, but has been surpassed by several others non-normalized. When costs are normalized for wealth and inflation, it still ranks third today.[2]

The longest-known track for a single tornado is the Tri-State Tornado with a path length of 151 to 235mi (243 to 378km). For years there was debate whether the originally recognized path length of 219mi (352km) over 3.5 hours was from one tornado or a series. Some very long track (VLT) tornadoes were later determined to be successive tornadoes spawned by the same supercell thunderstorm, which are known as a tornado family. The Tri-State Tornado, however, appeared to have no gaps in the damage. A six-year reanalysis study by a team of severe convective storm meteorologists found insufficient evidence to make firm conclusions but does conclude that it is likely that the beginning and ending of the path was resultant of separate tornadoes comprising a tornado family. It also found that the tornado began 15mi (24km) to the west and ended 1mi (1.6km) farther east than previously known, bringing the total path to 235mi (378km). The 174mi (280km) segment from central Madison County, Missouri to Pike County, Indiana is likely one continuous tornado and the 151mi (243km) segment from central Bollinger County, Missouri to western Pike County, Indiana is very likely a single continuous tornado. Another significant tornado was found about 65mi (105km) east-northeast of the end of aforementioned segment(s) of the Tri-State Tornado Family and is likely another member of the family. Its path length of 20mi (32km) over about 20 minutes makes the known tornado family path length total to 320mi (510km) over about 5½ hours.[18] Grazulis in 2001 wrote that the first 60mi (97km) of the (originally recognized) track is probably the result of two or more tornadoes and that a path length of 157mi (253km) was seemingly continuous.[19]