A prolonged and widespread tornado outbreak affected a large portion of the United States in late-May 2013 and early-June 2013.

The outbreak was the result of a slow-moving but powerful storm system that produced several strong tornadoes across the Great Plains states, especially in Kansas and Oklahoma.

[1] The twister was responsible for eight deaths, including famous storm chaser Tim Samaras, his son Paul, and Carl Young as a result of being caught off-guard by the tornado's unprecedented width.

On May 22, an upper-level low moved eastward over the Western United States, with forward progression limited by a blocking high around the Northern Plains and Great Lakes.

[7] With ample low-level moisture streaming north ahead of the low into an area of moderate instability, scattered severe weather was anticipated over parts of Colorado, Kansas, and Nebraska starting on May 24.

While the Storm Prediction Center only issued a slight risk that day, widespread tornadoes touched down in several states, some strong to violent.

[14] An even larger tornado, an EF3 wedge that was over a quarter mile wide, touched down just west of Bennington, and remained nearly stationary in a field for over an hour.

A total of six tornadoes were confirmed to have touched down in areas near Flint, two of which reached EF2 intensity and caused significant damage.

With the presence of an extremely unstable air mass over central Oklahoma, the Storm Prediction Center issued a Particularly Dangerous Situation Tornado Watch for much of the state during the afternoon of May 31 and lasting into the night.

[28][29][30] A large, very slow-moving, and erratic tornado remained on the ground for just over an hour as it executed a cyclonic loop in Ottawa County south of the town of Minneapolis and west of Bennington.

As the tornado reached the northern end of the track (its strongest point), it swept away a machinery shed, with one combine harvester stored inside being thrown and torn apart.

Despite the downgrade, the National Climatic Data Center maintains that the Bennington tornado was violent, and likely reached EF4 intensity at some point in its life.

Due to the tornado's slow motion, several areas in its path were likely exposed to winds well in excess of 100 mph (160 km/h) for at least 45 minutes.

Remaining over mostly open terrain, it did not impact many structures; however, measurements from mobile Doppler radars revealed extreme winds in excess of 313 mph (504 km/h) within the tornado.

[39] Although the tornado remained over mostly open terrain, dozens of storm chasers unaware of its immense size were caught off-guard.

[41] Other storm chasers, including The Weather Channel's Mike Bettes as well as Reed Timmer, were either injured or had their vehicles damaged.

[42][43][44] This large rain-wrapped tornado touched down at 7:50 p.m. CDT (0050 UTC) on May 31, southwest of Weldon Spring in St. Charles County, Missouri.

The tornado reached its maximum intensity to the east-northeast of Weldon Spring, west-southwest of St. Charles and Harvester, and south of St. Peters.

Three adjacent frame homes at this location sustained total loss of their roofs and exterior walls, and this small pocket of damage was rated EF3.

The roof was damaged and windows were broken at an ITT Technical Institute building and a vehicle was flipped in the parking lot.

Trees and power lines were downed and several homes and commercial buildings were damaged at mainly EF1 strength in nearby Bridgeton to the east of SSM DePaul Health Center.

Louis International Airport in Berkeley (which had previously taken a direct hit from an EF4 tornado on April 22, 2011), causing tree and power pole damage.

The tornado moved into residential areas on the northern side of Ferguson, downing trees and power poles, a few of which landed on homes and cars.

The flooding combined with damage from the tornadoes complicated efforts of emergency services personnel to render aid to areas impacted by the storm.

[55][56] Missouri authorities confirmed three deaths as a result of high water that occurred in the counties of Lawrence, Miller and Reynolds.

[58] On May 31, the National Oceanic and Atmospheric Administration (NOAA) announced it would no longer furlough employees under sequestration due to the outbreak of tornadoes.