A second day of powerful storms and severe weather unleashed a massive amount of destruction on parts of Oklahoma, including a mile-wide tornado Monday afternoon.
The same swath of Midwest states frequently face these deadly phenomena, which have so far left buildings and neighborhoods in their wake.
Here are some fast facts about severe weather from the National Oceanic and Atmospheric Administration :
What is a tornado?
A tornado is a narrow rotating column of air that extends from the base of a thunderstorm to the ground. Tornadoes can be difficult to see as the air is invisible. They become visible when they fill with condensation and debris.
Where is tornado alley?
Tornado Alley is a nickname given to an area of the United States where a high amount of tornadoes occur each year. Tornados can happen anywhere.
How many tornadoes occur in the U.S. each year?
About 1,200 tornados hit the United States each year. Records only date back to the 1950s.
Is there a tornado season?
The Southern Plains usually sees the most tornados between May and June, whereas along the gulf coast, high season is earlier in the Spring.
How is a tornado strength rated?
A tornado's size is usually categorized as an "EF- "followed by a number. This is called the "Enhanced Fujita Scale" which was created by the National Weather Service in 2007. The older rating system referred to tornados as F- then follow by a number. The EF system uses variables such as wind speed and damage.
What is the difference between a Tornado WARNING and Tornado WATCH?
A Tornado Watch refers to weather conditions that are favorable to produce a tornado. This is usually issued by the NOAA Storm Prediction Center. A watch is given to allow residents to prepare for severe weather and stay alert.
A Tornado Warning is issued by a state's local NOAA National Weather Forecast center by meteorologists. A Warning means a tornado has been spotted by a storm chaser or indicated by radar.
All information provided courtesy of the NOAA's National Severe Storms Laboratory .