The tornado frequency increases in the spring as the warm and cold seasons battle it out in the U.S.
Warm, humid air surges into the South during the spring months, while colder air remains in place across the northern tier of the country. The clash of warm, humid air and cooler, drier air to the north creates instability for thunderstorms to develop.
Another key ingredient for severe thunderstorm and tornado development is a powerful jet stream, or a corridor of fast winds around the altitude where planes fly. When there are powerful winds high in the atmosphere and weaker winds at the surface, a twisting motion in the atmosphere can help to produce rotating thunderstorms capable of spawning tornadoes.
During the spring months, the jet stream is often still potent across the U.S. before it shifts too far to the north during the summer to support violent storms with tornadoes touching down.
The sun's rays are also strengthening during the spring months, promoting increased daytime heating that further reduces the instability of the atmosphere.
A change in the weather pattern will turn off arctic air invasions and allow the March sun to go to work over much of the central and northeastern United States next week.
People across the Midwest and Northeast will be bundling up as the first week of March comes to a close due to a southward push of arctic air.
Mushers around the world are preparing their dogs for the Iditarod, a 1,000-mile-long trek through Alaska that starts on March 7. What qualities make some dogs better adapted for this race?
A spring fever alert is being issued for the United Kingdom and western Europe this weekend with April-like warmth set to surge in.
Afghanistan, Pakistan and India will once again become the target of another storm, complete with snow, potentially flooding rain and thunderstorms.
In the wake of a storm that brought heavy snow to the southern New England coast on Thursday, milder air will follow by next week around Boston.
Goodland, KS (2007)
Last day of record 78 days with temperatures below 50 degrees.
Washington, DC (1821)
Second outdoor inauguration. President Monroe was sworn in under rain and snow. High of 28.
Eastern U.S. (1872)
Modern March cold wave: 3 degrees in eastern New York City -- lowest ever in March; Washington, DC, 6 degrees -- latest ever below 10 degrees; Philadelphia, PA, 5 degrees -- March record.