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.
The focus for severe storms will move into the Ohio Valley and resume over New York state on Wednesday.
So far this year California has seen 1,569 wildfires, 85 percent more than in an average year.
The Memorial Day weekend will begin cool, windy and rainy in New England and part of the mid-Atlantic.
GOES-East failed again late Tuesday. It is one of the main satellites meteorologists use for the eastern part of the United States and the tropical Atlantic.
Severe storms are shifting eastward Wednesday afternoon delivering strong wind, heavy rain and hail.
On the two-year anniversary of the EF-5 tornado that leveled Joplin, Mo., the town has deployed assistance to Moore, Okla.
Sichuan Province China (1986)
More than 35,000 homes and 7,700 acres of crops were destroyed by a devastating hailstorm. Reports indicated that 100 people were killed and 9,000 injured. (Reports vary as to the exact date of the hailstorm.)
San Antonio, TX (1998)
Very dry since April 1st - only 0.05 of rain.
Waterville, ME (1832)
Kennebec Flood discharged 140,000 cubic feet of water per second -- high stage not equalled until 1901, and not exceeded until 1936.