Relationships between cloud-to-ground (CG) lightning, as reported by the U. S. National Lightning Detection Network™ (NLDN), and surface rainfall, as reported by NWS Cooperative Observers, have been examined during the Great Flood of 1993. The daily precipitation volume per reported CG flash (CGF) over the Greater Upper Mississippi River Basin (GUMRB) ranged from 4.0 x 10⁴ to 4.3 x 10⁶ m³/CGF with a mean and median of 4.6 x 10⁵ and 1.9 x 10⁵ m³/CGF, respectively, during June, July, and August, 1993. The monthly rain volume per reported CG flash ranged from 6.3 x 10⁴ to 2.1 x 10⁵ m³/CGF with an overall mean of 1.8 x 10⁵ m³/CGF. Similar ratios were found for the Upper Mississippi River Basin (UMRB) that is imbedded within the GUMRB. For the entire summer season, there were about 6.5 x 10¹¹ cubic meters of rainfall over the GUMRB and there were 3.6 x 10⁶ CGF reported by the NLDN, which gives an overall seasonal mean of 1.8 x 10⁵ m³/CGF. If we correct the lightning counts for an imperfect NLDN detection efficiency, we estimate that there were actually about 5.4 x 10⁶ CG flashes over the GUMRB, and therefore, the actual seasonal mean rain volume was about 1.3 x 10⁵ m³ per CGF. The above values are remarkably similar to the summer mean of 1.1 x 10⁵ m³/CGF obtained by Petersen and Rutledge (1998) over the mid-continental U.S. and are consistent with other studies on daily and storm scales. The above ratios are larger than, but still consistent with, an estimate of the excess stream volume per excess (reported) CG flash from the UMRB, 6.8 x 10⁴ m³/CGF, based on streamflow measurements at Keokuk, IA.