00:48 Sioux Falls Tornado Rips Apart Building in Newly Released Footage Newly released footage from inside a health center in Sioux Falls shows the damage done by an EF-2 tornado that struck the city one year ago.

Severe thunderstorms and flooding rainfall swept through parts of the South from Wednesday, April 3, through Sunday, April 7.

(LATEST NEWS: Storms Damage Homes, Cancel Flights and Knock Out Power)

Wednesday, a supercell thunderstorm produced hail larger than baseball-size, damaged an outbuilding and downed power poles in Harmon County, Oklahoma.

Thursday morning, marble- to golf-ball-sized hail was reported in parts of Louisiana, East Texas and Oklahoma.

The bigger issue, however, was flooding rain.

Lake Charles, Louisiana, had been inundated with 6.42 inches of rain Thursday, the city's fourth-wettest April day on record and the wettest single day there since Harvey . This led to major flash flooding in the area, with one home reportedly flooded, according to KPLC-TV.

Severe thunderstorms Saturday rumbled through a swath from central and East Texas into northern Louisiana, Mississippi and northwestern Alabama.

A short-lived tornado was confirmed by radar in San Gabriel, Texas, early Saturday afternoon. This is about 45 miles northeast of Austin. Heavy rain flooded some roads just northeast of Austin.

Hail up to the size of softballs damaged vehicles in Grapeland, Texas, about 115 miles southeast of Dallas. Softball-sized hail also was documented in Alto, Texas .

Sunday morning, quarter-sized hail was reported in the far northern suburbs of San Antonio, Texas. A 73-mph wind gust was clocked in Harlingen, Texas . Some FEMA trailers were destroyed, and damage to the hangar roof was reported at an old Navy base near Youngeen, Texas.

In Deep South Texas, thunderstorm winds were strong enough to pick up a trampoline and toss it into a power pole in Santa Rosa Sunday morning. The National Weather Service said no one was hurt.

Streets were closed and vehicles stranded in floodwater near Whitsett, Texas, and a stretch of northbound Interstate 35 was flooded and closed on the northern side of Austin Sunday morning.

Damaging winds associated with a squall line of severe thunderstorms knocked down trees and power lines in the Houston metro area Sunday afternoon.

In Dayton, Texas, some 35 miles northeast of Houston, an 11-year-old girl was struck by lightning Sunday afternoon but was reportedly in good condition, the Liberty County Sheriff's Office told KTRK-TV.

Several large tree limbs were reported down on a residence in Beaumont, Texas, Sunday afternoon, according to the National Weather Service.

Hail reached the size of golf balls and eggs in Lexington, Mississippi, Sunday afternoon, damaging vehicles in the city.

A number of factors worked together to bring this uptick in severe weather.

The jet stream sent a number of waves, or disturbances, across the South.

Ahead of those disturbances, warmer and more humid air was pulled northward from the Gulf of Mexico.

Those disturbances, along with colder, drier air topping warmer, humid air, as well as air-lifting surface features such as a dryline and a frontal system, ignited some severe thunderstorms from Wednesday through Sunday.