By Raymond Britt -- Conditions on race day can affect Ironman triathlon outcomes, in terms of DNF (Did Not Finish) rates. Held in September and known for unpredictable weather, Ironman Wisconsin is one race where condition and DNF (Did Not Finish) rates have varied considerably from year to year. [Also see our North American Ironman DNF Rate Comparisons]
I've competed in five Ironman Wisconsins, from cool days to scorchers, from a low of 4% in the inaugural year (though 16% registered but did not start) to 19% in 2005. Competitors in 2003 and 2005 were faced with 90-100 degree conditions; 2006 was a freezing, rainy, awful day, while 2008 and 2009 were perfect. In recent years, the race norm seems to be a 10% to 12% DNS rate and a 5% to 6% DNF rate, which is reflected in our RunTri's Toughest 25 Ironman Triathlon analysis. Even in perfect conditions, Ironman Wisconsin rates a top 5 Most Difficult races rating.