A tornado is a rotating column of air, extending from the base of a cumuliform cloud, and often visible as a condensation funnel in contact with the ground, and/or attendant circulating dust or debris at the ground (WMO, 2017).

The strength of a tornado can be estimated from the degree of damage caused using the Enhanced Fujita scale (Wind Science and Engineering Center, 2004; National Weather Service, no date).

Tornadoes kill fewer than 100 per year on average but they can be very destructive and cause huge economic losses. The United States is a major hotspot with about 1,000 tornadoes every year, causing 80 deaths and more than 1,500 injuries on average (National Geographic, 2019).

Owing to the unpredictable nature of tornados, protecting the public is focused on education and outreach which provide information on the tornado as a threat, how to identify a tornado and practical measures on how individuals can protect themselves, and how to find and watch warning systems that alert the public (CDC, 2020).

Since the advent of Doppler Radar, lead times for tornado warnings have increased from when a tornado first touches the ground to upwards of 14 to 20 minutes or more beforehand (WMO, 2017b; National Geographic, 2019).

Risk factors

  • Lack of early warning systems and preparedness programmes.
  • Even when warning systems are in place, the aged and children have higher mortality rates.
  • Populations living in mobile homes are at greater tornado risk. The rate of serious injury for mobile homes occupants is 85.1 per 1,000 compared to 3 per 1,000 for occupants in standard homes.

Vulnerable areas

  • The most tornado-prone areas in the world are in North America, in particular the Great Plains in the United States and south-central Canada.
  • Tornado Alley, a region that includes eastern South Dakota, Nebraska, Kansas, Oklahoma, northern Texas and eastern Colorado, is home to the most powerful and destructive of these storms.
  • The United States gets 75 per cent of all the world’s tornadoes, followed by Canada and Bangladesh.
  • Australia, New Zealand, South Africa, India, Argentina and the Russian Federation are also prone to strong tornadoes.
  • Communities living in poorly built houses close to potential flying objects are in particular danger. People outdoors when tornadoes occur are at higher risk of mortality.

The Enhanced Fujita Tornado Scale

The Fujita Scale is named for Dr TT (Ted) Fujita, who made the first systematic study of tornado forces; it was replaced by the Enhanced Fujita (EF) Scale in February 2007.

Risk reduction measures

  • Monitoring systems to observe thunderstorms with radar and receive reports on tornadoes.
  • A hazard map to identify risk and vulnerability.
  • A warning/communication system to alert people in the path of a tornado.
  • Underground shelters to protect people.
  • Avoiding mobile home settlements in risky zones.
  • Education and awareness about tornadoes, warnings and safe action.

Latest Tornado additions in the Knowledge Base

The growing threat of tornadoes in US eastern states has prompted calls for better preparedness, and in particular the need for more storm shelters.
British Broadcasting Corporation (BBC)
Documents and publications
This study examines factors shaping individuals' preferences for use of tornado shelters in public and private facilities during the COVID-19 pandemic, utilizing over 6000 surveys collected in Spring and Summer 2020 across the United States.
A resilient surface frontal zone lying between the Rockies and Appalachians has been oscillating north and south during much of May.
Yale Climate Connections
Research briefs
In her most recent study, Armstrong found that roughly 50% of those surveyed in the mid-south could not accurately define a tornado warning.
University of Nebraska-Lincoln
AI for DRR
TorNet, a public artificial intelligence dataset, could help models reveal when and why tornadoes form, improving forecasters' ability to issue warnings.
MIT Press, the
Spring is tornado season in the U.S., but the tornadoes in Nebraska and Iowa were quite a bit farther north and east of what would be typical for tornadoes in late April, when tornado activity is more common in Oklahoma and Texas.
Conversation Media Group, the
Tornado going over land close to a house.
Two experts ponder the social and physical factors that may shape the next colossal onslaught of twisters.
Yale Climate Connections
The warning time before a tornado touches down is measured in minutes. Long-term planning on the sunny days when tornadoes aren’t a threat is crucial for preparing for and recovering from these storms.
Florida State University

Is this page useful?

Yes No
Report an issue on this page

Thank you. If you have 2 minutes, we would benefit from additional feedback (link opens in a new window).