How do we know?
↻ One of the pages with a moving picture
Radar sees the spinning winds, and volunteers watch the sky.
- Near the ground, wind blows slowly one way. Higher up, it blows faster or another way. This is called wind shear.
- Between them, an invisible tube of air starts to spin on its side.
- A thunderstorm’s rising air tilts the tube upright. Now the whole storm spins. It is called a supercell.
- Scientists think the spin can then tighten into a tornado. Exactly how is still not fully understood.
Doppler radar can spot a tornado’s spinning winds. But radar can’t see every tornado, so trained volunteer storm spotters, called SKYWARN, watch the sky too.
On 3 May 1999, radar measured winds of 318 mph at Bridge Creek and Moore, Oklahoma. That is the fastest ever measured in a tornado.
Tornadoes are not only an American thing. Outside the United States, Bangladesh is one of the places with the most tornadoes.
Wow number
1,200 tornadoes hit the United States in a typical year. That’s more than three a day!
Myth or fact?
A tornado has a calm eye in the middle, like a hurricane. Myth. There is no eye. That idea came from a movie.
North of the equator, most tornadoes spin counterclockwise. Fact. More spin that way than clockwise.
Think about it
As few as 1 in 5 spinning supercell storms makes a tornado. What might be different about the ones that do?
Where in the world?
Moore, Oklahoma, USA where radar measured winds of 318 mph on 3 May 1999, the fastest ever measured in a tornado. Bangladesh is another place with many tornadoes — 35.3395° N, 97.4867° W.
Where these facts come from
Every number on page 37, and who measured it
This page explains wind shear, the spinning tube and supercells.
Severe Weather 101: Tornado Types — NOAA's National Severe Storms Laboratory, U.S. storm scientists
nssl.noaa.gov/education/svrwx101/tornadoes/types
We checked it on 31 October 2026
This page tells us how many tornadoes hit the U.S. each year, and where else they are common.
Severe Weather 101: Tornado Basics — NOAA's National Severe Storms Laboratory, U.S. storm scientists
nssl.noaa.gov/education/svrwx101/tornadoes
We checked it on 31 October 2026
This page tells us about the 318 mph tornado winds, radar, storm spotters and the tornado-eye myth.
Severe Weather 101: Tornado FAQ — NOAA's National Severe Storms Laboratory, U.S. storm scientists
nssl.noaa.gov/education/svrwx101/tornadoes/faq
We checked it on 31 October 2026
This page tells the story of the May 3, 1999, Oklahoma tornadoes.
The Great Plains Tornado Outbreak of May 3-4, 1999 — The U.S. National Weather Service
weather.gov/oun/events-19990503
We checked it on 31 October 2026
This page tells us which way most tornadoes spin.
Tornado Frequently Asked Questions — NOAA's Storm Prediction Center, the U.S. tornado and storm forecasters
spc.noaa.gov/faq/tornado
We checked it on 31 October 2026
Has this changed?
Scientists do not yet fully understand how a spinning storm tightens into a tornado, so this answer may grow.
Radar and storm spotters keep getting better at warning people.
Words from this page
- wind shear
- When wind blows at different speeds or in different directions at different heights.
- supercell
- A thunderstorm whose whole body is spinning.
- vortex
- A spinning funnel of air or water.
Try it!
Make a tornado in a bottle.
1. Fill a plastic bottle two-thirds full with water. With a grown-up, tape an empty bottle on top, mouth to mouth. 2. Flip it over and swirl it in circles. 3. Watch the water drain down.
What happens: a spinning funnel, called a vortex, forms as the water swirls down.
Go further