ng4_501

An F3 Category tornado swirls across a South Dakota prairie. Tornadoes are classified according to their wind speeds, from weak F0 tornadoes with 40 to 72 mph (64 to 116 kph) winds, to ferocious F6s, with 319 to 379 mph (513 to 610 kph) winds. At F3, this tornado’s winds clocked in between 158 and 206 mph (254 to 332 kph).