Source:  Storm Prediction Center (National Weather Service; 2013 tally here); AnalysisWire Research

Note:  Prior Years refers to the years 1950 – 2012, the years of the most accurate tornado data.  May 31 tornado fatalities could be increased.  The tally we use is currently 9, which may be too low.  The tally is currently at 20, according to NewsOK.com, but some of these fatalities may be due to flooding rather than tornadoes. The Storm Prediction Center is explicit about using deaths caused only by tornadoes in its data rather than deaths caused by flooding, so we are being cautious in keeping the May 31 death toll at 9 for the time being. Tornado statistics are in beta and are subject to change.