It has been suggested that excess cloud condensation nuclei from the eruption were responsible for the Great Flood of 1993 in the Midwestern United States.

Soils across much of the affected area were saturated by June 1, with additional rainfall all running off into streams and rivers, instead of soaking into the ground.

Portions of east-central Iowa received as much as 48 inches (120 cm) of rain between April 1 and August 31, 1993, and many areas across the central-northern plains had precipitation 400–750% above normal.

[citation needed] Emergency officials estimated that nearly all of the 700 privately built agricultural levees were overtopped or destroyed along the Missouri River.

Navigation on the Mississippi and Missouri River had been closed since early July, resulting in a loss of $2 million (1993) per day in commerce.

In an attempt to strand his wife on the other side of the river so he could continue partying, Scott allegedly removed several sandbags from a levee holding back the water.

From May through July, Sioux Falls, South Dakota received 22.55 inches (573 mm) of rain, the wettest three-month period in its history.

These breaches acted to delay the flood crests, temporarily storing excess water in the adjacent lowlands, but the rain kept falling.

During the second week of June, river levels rose to near flood stage before yet again beginning their slow recession.

On July 9, four buildings on Iowa State University's campus flooded; resulting in over 1.4 million dollars in estimated damages and six weeks of construction to reopen.

That same day President Bill Clinton toured Iowa's capitol and neighboring cities alongside Governor Terry Branstad.

Navigation on the Mississippi and Missouri River was closed in early July, resulting in a loss of $2 million (1993) per day in commerce.

[citation needed] The crests, now combined as one, moved downstream through St. Louis on the way to the Upper Mississippi's confluence with the Ohio River at Cairo, Illinois.

Only minor flooding occurred below Cairo due to the Lower Mississippi's larger channel below that point, as well as drought conditions in the eastern U.S.

The released water continued to flow parallel to the river, approaching the levees protecting historic Prairie du Rocher and Fort de Chartres.

Approximately 100,000 homes were destroyed as a result of the flooding, 15,000,000 acres (23,000 sq mi; 61,000 km2) of farmland inundated, and the whole towns of Valmeyer, Illinois, and Rhineland, Missouri, were relocated to higher ground.