There was a M2.7 in last hour near St. Louis near Mississippi river, well away from New Madrid zones, so probably in Wabash. The river at St Louis is just below flood stage. The river farther upstream is in Major flood. L. Seeber suggested that river stage might be a better comparison than rainfall because it may be more related to water table. But, I think one would have to do small rivers because it can be dry in an area along the Missouri, Ohio, Mississippi, with high stages due to rain etc upstream. If trying to do monthly or quarterly comparisons, river stage may not be the way to go because they rise and fall on that period. So, stick with rainfall in my opinion.

(qualification: quakes in last hour sometimes go away).
Chris