A significant and destructive tornado outbreak that affected parts of the Midwestern United States and lower Great Plains in mid-May 2013.

During this nearly two-week-long event, the Storm Prediction Center (SPC) received 1,967 reports of severe weather: 101 for tornadoes, 1,176 for wind, and 690 for hail.

The SPC issued a small slight risk for severe thunderstorms around the Black Hills into central Nebraska, with the main threat being large hail and the possibility of an isolated tornado.

Extreme instability ahead of it, with CAPE values reaching 4,000–5,000 J/kg along with strong diabatic heating, was anticipated to spark widespread severe thunderstorms and some supercells.

[22] The first tornado watch was issued at 2:45 p.m. CDT (1945 UTC) for much of western Nebraska, Kansas, and extreme northeast Colorado as moist northerly flow ahead of the trough met up with a dry line moving into the region.

A large plume of steep mid-level lapse rates accompanied by deep moisture (with dew points in some areas exceeding 70 °F (21 °C)) spread across much of the central and southern plains into the Mississippi River Valley.

The most intense storms were anticipated over the southern Missouri River Valley where strong daytime heating and "aggressive destabilization" would take place.

In light of that, the SPC issued a moderate risk of severe thunderstorms for south-central Oklahoma, eastern Kansas, western Missouri, and extreme southeastern Nebraska.

[30] Further south in Oklahoma, a rapidly mixing dry line accompanied by a deepening surface low moved eastward into an area with deep moisture.

Maximized pressure falls ahead of the dry line allowed several storms to acquire intense updrafts and develop into rotating supercells within the state.

[39] Further north over parts of Iowa and Minnesota, a mid-level vortex over the region accompanied by scattered thunderstorms presented a risk of severe storms.

[44][45] Severe activity began decreasing by 10:00 p.m. CDT (0300 UTC) as the main squall line over Missouri entered an area of increased capping.

The Storm Prediction Center issued a moderate risk of severe thunderstorms during the early morning hours of May 20 from southeastern Missouri to north-central Texas, for the possibility of isolated strong tornadoes across central and eastern Oklahoma, in addition to the threat of large hail and damaging straight-line wind gusts.

Strong instability ahead of the system prompted the SPC to issue a moderate risk of severe thunderstorms for extreme southeast Oklahoma, southwest Arkansas, northwest Louisiana, and northeast Texas; however, the main threat was damaging winds rather than tornadoes.

Activity was expected to be scattered at first, with some isolated supercells capable of producing tornadoes, but a squall line was anticipated to develop quickly and become the dominant feature.

Moderate instability, with CAPE values ranging from 1,000 to 2,000 J/kg and steep lapse rates were supporting of damaging straight-line winds, especially across Michigan, New York and Massachusetts.

Situated over the ocean, a continuous stream of Atlantic moisture was brought over the Northeast, resulting in "anomalously cold temperatures" and prolonged heavy precipitation.

[74][75] At 6:00 p.m. CDT (2300 UTC) on May 19, a tornado touched down along the western shore of Lake Thunderbird in eastern Cleveland County (east of Norman).

The tornado widened and weakened back to EF2 strength as it crossed S Harrah Rd, completely destroying several mobile homes and outbuildings in that area.

The tornado later dissipated at 6:50 p.m. CDT (2350 UTC) about 6.5 miles (10.5 km) southeast of McLoud, after causing some additional minor tree damage along Coker Rd.

[86] Sixteen minutes later, a tornado touched down roughly 3 miles (4.8 km) northwest of the center of Newcastle in McClain County.

After crossing the Interstate 44 bridge over the Canadian River, the tornado turned east and tracked directly through South Oklahoma City and Moore, producing a large swath of catastrophic damage through densely populated areas.

[87] Based on multiple instances of well-built, anchor-bolted brick homes being completely swept away in Moore, along with the presence of severe ground scouring, wind-rowing of structural debris, and large multi-ton objects being lofted long distances through the air, it was estimated that the tornado had peak winds of 210 mph (340 km/h).

[94] The heaviest rains fell across parts of North Dakota, with accumulations amounting to 9.5 inches (240 mm) near Milton in Cavalier County over a three-day span.

[98] With fears of the dam collapse in North Dakota, the National Guard was deployed to Cavalier in order to construct emergency levees.

[80] The following day, President Barack Obama signed a major disaster declaration for Cleveland, Lincoln, McClain, Oklahoma and Pottawatomie counties.

[116][117] This allowed for federal aid to be sent to residents in the hardest-hit areas of Oklahoma and gain access to temporary housing, home repairs, and low-cost loans.

[121] In Shawnee, the Southern Baptist Disaster Relief, the Salvation Army, and Red Cross provided free meals to first responders and displaced residents.

[122] In the wake of the Moore tornado, there were rumors that relief organizations were relocated from communities in Shawnee; however, the Salvation Army and local news agencies confirmed that residents in the area were getting proper assistance.

[106] Following the assessments, Chittenden, Essex, and Lamoille Counties were declared major disaster areas on June 13, allowed residents to receive federal aid.