The largest tornado outbreak on record for a single 24-hour period, the Super Outbreak occurred on April 3 and 4, 1974. During that time, nearly 150 tornadoes swept across 13 central and eastern US states as well as Ontario, Canada, severely damaging approximately 900 square miles (2,330 sq km) along a total combined path length of 2,600 miles (4,180 km). The outbreak brought more violent tornadoes than had ever been observed, including 23 F4 tornadoes and how many F5s? Discuss
Source: The Free Dictionary