Significant rainfall led to an above average runoff in the upper Missouri River Basin. June runoff was 6.6 million acre-feet, which is 119% of average and 2.6 MAF higher than forecast.
A strong weather system moved into the basin on June 21 producing excessive rainfall in eastern South Dakota, north central and northeastern Nebraska, and northwestern Iowa. The rainfall totals exceeded 600% of normal over the 24-hour period.