[2] This severe weather outbreak can be traced back to a powerful, slow-moving low pressure area with a warm front to the north over Nebraska and Missouri.

All of the ingredients were present in the atmosphere for the developing of supercell thunderstorms producing damaging wind, large hail and tornadoes.

[5] The Storm Prediction Center issued a moderate risk for severe weather across western Kansas and small portions of Oklahoma, Colorado and Nebraska for May 4, while temperatures were in the mid to high 80s°F (near 30 °C).

The atmosphere remained capped for much of the day, but storms began to develop in the late afternoon hours in western Oklahoma and the eastern Texas Panhandle.

[9] The most intense activity took place during the late afternoon and evening hours as supercells developed along a long line from South Dakota to North Texas.

Nonetheless, the SPC issued a moderate risk for severe storms over parts of central Kansas and northern Oklahoma as the trough remained in place.

Several storm chasers captured the formation of a tornado south of Greensburg around 9:20 pm CDT (0220 UTC),[15] which apparently strengthened as it neared Greensburg and began moving due-north towards the town, and at 9:38 pm CDT (0238 UTC), storm chasers reported that it had grown to over 1/2 mile in diameter.

Eyewitnesses and storm chasers reported that multiple vortices were circulating around the perimeter of the large, wedge-shaped tornado during its early stages.

Several farmsteads along the highway were damaged or destroyed, livestock was killed, and trees were denuded and debarked in this area as well.

At 9:41 pm CDT (0241 UTC) the National Weather Service office in Dodge City issued a tornado emergency for Greensburg.

Multiple homes, including an entire row of seven adjacent residences, were swept completely away and scattered across a field in this area at the south edge of town.

[20] Two schools, a Tractor Supply Company store, the Greensburg City Hall and other businesses fell victim to the violent winds and were destroyed or flattened.

[20] The Kiowa County Memorial Hospital was severely damaged at EF3 intensity, and a 4.9-ton reinforced concrete beam was lifted from the structure and thrown onto a nearby vehicle.

A large brick Mennonite Church in this area was completely leveled with the foundation partially swept clean of debris, vehicles were thrown and mangled, trees sustained complete debarking, and severe ground scouring occurred before the tornado left the city limits.

[28] Southeast of Macksville, yet another large EF3 wedge tornado developed and quickly grew to just under a mile wide as it moved northeast.

[32][33] Across portions of eastern Nebraska and western Iowa, rainfall amounts exceeded locally 6 inches (152 mm).

[40][41] The heavy rains also affected activities surrounding the Riverfest (Wichita River Festival) which postponed some events until May 14.

[43] In Aberdeen, South Dakota, 7.75 inches (197 mm) of rain fell the evening of May 5 into the early morning hours of May 6, causing significant flooding in some areas around the city.

[44] The highest unofficial rainfall total was reported in Epiphany, South Dakota where as much as 10 inches (254 mm) fell during the weekend.

[46] In southern Oklahoma City and surrounding communities, strong straight-line winds caused damage to several buildings and downed trees and power lines in the early morning hours of May 7, with cleanup efforts being complicated due to flooding rains accompanying the storm.

Over 100 Red Cross officials were called in while some worked with the Federal Emergency Management Agency for the recovery efforts.

[50] After the tornado, looting was reported in the community and at least seven suspects, including four soldiers that were not part of the relief effort and went to Greensburg on their own, were arrested and faced charges of burglary and theft.

[55] Kansas Governor Kathleen Sebelius and President George W. Bush both declared Kiowa County a disaster area.