Tornado

Prior to 2003, the single most violent tornado in United States history was the Tri-State tornado on March 18, 1925. Beginning in Missouri, the tornado stayed on the ground for over 220 mi (350 km), crossing Illinois, moving into Indiana, and leaving a trail of damage over one mile (1.6 km) wide in places. Tornado damage often is limited since they usually strike unpopulated areas, but the Tri-State tornado plowed through nine towns and destroyed thousands of homes. When the storm was over, 689 people had lost their lives and over 2,000 were injured making the Tri-State the deadliest tornado on record.

On May 3, 1999, a storm started in southwestern Oklahoma, near the town of Lawton. By late in the day, it had grown into a violent storm system with 76 reported tornadoes. As the storm system tore across central Oklahoma and into Kansas, over 43 people were killed, over 500 injured and more than 1,500 buildings were destroyed. One of the tornadoes, classed as a F-5, was as much as a mile wide at times and stayed on the ground for over four hours.

Another historic storm was the severe tornado outbreak of April 3-4, 1974. As a strong low pressure system moved over the Midwest, an advancing cold front ran into warm Gulf air over the southern states. The resulting storm triggered 148 tornadoes over 13 states in the next 24 hours, some reaching F4 and F5 in strength. As severe as this outbreak was, the death toll was less than half of that from the Tri-State tornado because of advances in tornado forecasting and warnings.