Why the Oklahoma Tornado Was Among the Worst Ever

The monster tornado that tore through an Oklahoma City suburb is one of the worst on record by most standards, the Smithsonian finds. At an estimated two miles wide, the storm was one of the biggest recorded and it was also extremely powerful, with winds above 199mph. But what made it especially deadly was its duration—it was on the ground for 40 minutes, while most tornadoes only last for a few minutes.

• The strongest tornado ever recorded, with winds of 302mph, struck May 3, 1999, in Moore, Okla., the same place that was devastated by yesterday's tornado, the Atlantic notes.
• The 1999 Oklahoma tornado was the deadliest since a tornado in Wichita Falls, Texas, killed 42 people on April 10, 1979, but it has been surpassed by several since, including the May 22, 2011, tornado that killed 158 people in Joplin, Mo.
• The worst tornado on record in the US was the "Tri-State" tornado that killed 695 people in Missouri, Illinois, and Indiana on March 18, 1925. That storm stayed on the ground for three and a half hours and killed 234 people in Murphysboro, Ill., alone.

(More tornado stories.)