Tornadoes are one of nature's most violent storms. In an average year, 800 tornadoes are reported across the United States, resulting in 80 deaths and over 1,500 injuries. A tornado is as a violently rotating column of air extending from a thunderstorm to the ground. The most violent tornadoes are capable of tremendous destruction with wind speeds of 250 mph or more. Damage paths can be in excess of one mile wide and 50 miles long.Tornadoes come in all shapes and sizes and can occur anywhere in the U.S at any time of the year. In the southern states, peak tornado season is March through May, while peak months in the northern states are during the summer.

The Widespread Tornado Outbreak of April 3-4, 1974

It was the worst tornado outbreak in U.S. history with 148 twisters touching down in 13 states. Before it was over 16 hours later, 330 people were dead and 5,484 were injured in a damage path covering more than 2,500 miles. Twenty-five years ago, National Weather Service forecasters could see only green blobs on their radar scopes and had to wait for visual confirmation of the tornado before issuing a tornado warning. Today's forecasters, thanks to a $4.5 billion weather service modernization effort, view evolving storms in graphic detail and can now issue warnings before tornadoes even form, with an average lead time of 11 minutes.

"Deadly storms such as the 1974 super outbreak can and will happen again," said Ken Haydu, meteorologist in charge of the National Weather Service's forecast office in Wilmington, Ohio. "The people who experienced the super outbreak have an important story about tornado awareness and preparedness to pass on to later generations." In all, 13 states were struck by twisters: Alabama, Georgia, Illinois, Indiana, Kentucky, Michigan, Mississippi, North Carolina, Ohio, South Carolina, Tennessee, Virginia, and West Virginia.

1900-1909:

The outbreak of April 24-26, 1908, included violent tornadoes that moved through parts of Louisiana, Mississippi and Alabama, killing 324 people and injuring 1,652 others. The worst damage took place in Amite, La., where 29 people died.

1910-1919:

A long-track tornado on May 26, 1917, traveled across Illinois and Indiana for 293 miles, lasting seven hours and 20 minutes. The tornado killed 101 people and injured 638 others. Another tornado moved through the town of Matoon, Ill., destroying everything in a two and a half block-wide path for 2.5 miles.

1920-1929:

The Tri-State tornado of March 18, 1925, developed near Ellington, Mo., and then for the next 3.5 hours killed more people and destroyed more schools, homes and farmsteads thanany other tornado to this point in history. The tornado cut across southern Illinois into southern Indiana, killing 695 people, 234 of them in the town of Murphysboro, Ill., and injuring 2,027. Other tornadoes occurred in Kentucky, Tennessee and Alabama. A total of nine tornadoes were reported, leaving 747 dead and nearly 2,300 people injured.

1930-1939:

On March 21-22, 1932, a total of 330 people died as a result of tornadoes that touched down across northern Alabama. One tornado hit the northeast part of the state, killing 38 and injuring 500. During the Tupelo/Gainesville outbreak on April 5-6, 1936, 17 tornadoes were scattered across parts of northern Mississippi and northern Georgia. A massive pair of tornadoes hit Gainesville, Ga., in the morning, killing 203 people and causing 1,600 injuries.

1940-1949:

Three major outbreaks occurred during this decade. The first, on March 16, 1942, left 152 dead and 1,284 injured from tornadoes that raked across parts of Illinois, Mississippi, Tennessee and Kentucky. As many as 63 people perished in a tornado northwest of Greenwood, Miss., that hit as buses carried school children home. Five hundred people were injured. A total of 154 people died and nearly 1,000 were injured on June 23, 1944, as tornadoes struck parts of Ohio, Pennsylvania, West Virginia, Maryland and Delaware. The worst areas affected were parts of northeast West Virginia and western Maryland, where a tornado family killed 30 and injured 300. On April 9, 1947, a tornado outbreak that included eight tornadoes raked across parts of Texas, Oklahoma and Kansas. One tornado killed 107 people in Woodward, Okla. Devastation covered 100 city blocks and 1,000 homes were damaged or destroyed. Cost of the damage at that time was estimated at $6 million. Clean-up afterward was hampered by cold and snow.

1950-1959:

On May 11, 1953, a violent tornado hit downtown Waco, Texas, killing 114 people and destroying about 200 business buildings. Heaps of bricks up to five feet high filled the streets. Survivors were buried for up to 14 hours. A tornado outbreak in early June 1953 produced two major tornadoes. On June 8, a tornado hit in Flint, Mich., leaving 116 people dead. The next day, June 9, a tornado described as "a huge cone of black smoke" carrying debris eastward over the Boston area and out over the Atlantic Ocean caused 94 deaths and nearly 1,300 injuries in Worcester, Mass. In the United States, the death toll was 116 from tornadoes in Michigan, Ohio, Massachusetts and New Hampshire. Other tornadoes occurred in Canada. The hardest-hit area from a tornado outbreak in Oklahoma and Kansas on May 25, 1955, was Udall, Kansas. Eighty people were known dead and 270 were injured, which was more than half of the people in Udall, and the town was destroyed. For the entire outbreak, tornadoes killed 102 people and injured 563. A tornado moved across southeast parts of Kansas City hitting the area of Ruskin Heights on May 20, 1957. Forty-four people were killed and 531 were injured. More than 825 homes and businesses were damaged or destroyed, including the local high school. The outbreak itself spread from northeast Kansas and northeast Oklahoma through Missouri into Iowa and Illinois. In all, 17 tornadoes killed 59 people and injured 665 others.

1960-1969:

The second most damaging outbreak of the century, known as the Palm Sunday outbreak, occurred April 11-12, 1965. Nearly 50 tornadoes struck parts of the Great Lakes region fromWisconsin and Illinois eastward through lower Michigan and northern Ohio. The outbreak resulted in 256 deaths and 3, 402 injuries. Twin tornadoes moved into Goshen, Ind., destroying nearly 100 trailer homes. A large tornado hit Russiaville, Ind., damaging or destroying 90 percent of the buildings. As many as 44 people died and 612 were injured as one tornado followed another tornado across Steuben and Monroe Counties in lower Michigan. Tornadoes devastated areas in northern Toledo, Ohio, killing 18 people. Other tornadoes moved through areas about 15 miles southwest of Cleveland just northeast of Strongsville. Six homes literally vanished, 18 people were killed and 200 others were injured.On June 8, 1966, a tornado brought massive damage to Topeka, Kansas, causing $100 million in damage. This became the most expensive tornado to date.

1970-1979:

The most prolific tornado outbreak of the 20th century was the Super Outbreak of April 3-4, 1974. During a 16-hour period, 148 tornadoes occurred from Illinois and Indiana into Michigan and Ohio southward through the Tennessee Valley into Mississippi and Alabama. This outbreak produced the largest number of tornadoes, with 30 causing F4 damage or worse. On one occasion, as many as five large tornadoes were on the ground at one time. The outbreak killed 315 people and resulted in 6,142 injuries. One tornado hit Xenia, Ohio, at 4:30 p.m., moved through the center of town and demolished the high school. Thirty-four people died and 1,150 were injured in Xenia as 300 homes were destroyed and 2,100 homes were damaged. Five years later, a tornado hit Wichita Falls, Texas, on April 10, 1979, killing 42 people and injuring 1,740.

1980-1989:

Thirty tornadoes spread out across parts of northeast Ohio into western Pennsylvania on May 31, 1985. The outbreak killed 76 people and injured 876 others. Twelve people died from one tornado that moved from Ashtabula County, Ohio, into Erie County, Penn. Sixteen people were killed by a tornado that started over Trumbull County, Ohio, then moved east/northeast across parts of Pennsylvania. Another outbreak moved across Iowa and Minnesota into Wisconsin on June 7-8, 1984. The town of Barneveld, Wisc., was hit by a tornado just before midnight. All but the water tower was demolished and nine people were killed. As many as 45 tornadoes in the entire outbreak killed 13 people.

1990-1999:

The role of video tape and the advances in media technology provided many breath-taking views of tornadoes in the 1990s. People came from miles around to film the Hesston, Kansas, tornado on March 13, 1990. One tornado started near Goshen, only to merge with a second near Hesston and track northeast to just southwest of Topeka, Kansas. Another notable Palm Sunday tornado occurred on March 27, 1994, when 22 people died in Goshen, Ala., after a tornado hit a church. Most recently, a large tornado mowed through areas of southwest Oklahoma City and Moore, Okla., on May 3, 1999, demolishing or damaging more than 8,000 homes and ringing up more than $1 billion in damage. This tornado was part of an outbreak of 74 tornadoes that affected parts of Oklahoma and southern Kansas, killing 48 people. Advancements in communications through radio and television helped issue advanced watches and warnings to the public. Plus, meteorological advancements from research in storm structure using Doppler radar helped forecasters identify tornadic storms, improving warnings from a few minutes to as many as 20 minutes and increasing public response.