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.
On the heels of Danielle, another weak tropical system will move onshore from the Gulf of Mexico with drenching downpours and the risk of flash flooding.
The risk of thunderstorms and severe weather will return to the north-central United States this weekend, including some areas that were hit by violent storms on Wednesday.
At least 23 people have died in West Virginia as a result of extreme flooding that inundated portions of the state on Thursday.
Showers threaten to cause delays on a nearly daily basis next week at the 2016 Wimbledon Championships.
After dealing with heavy thunderstorms and heat to start the weekend, Germany will welcome more seasonable temperatures and fewer downpours early next week.
El Niño officially came to an end in early June, and experts are calling for a La Niña to develop in its footsteps.
Holden Beach, NC (1994)
76 mph wind gust in a thunderstorm.
Lancaster, PA (2000)
5.67" of rain in 4 hours.
"A general fast on ye account of ye drought." Very dry spring; villages caught on fire.