Dusting of snow on summit of Mt. Bohemia on October 10, 2009. But since that date is already taken, I will go with unlucky November 13.
Groomed skiing at Michigan Tech on November 13, 2012.
An interesting wager, since oftentimes Mohawk can be a bit of an early season banana belt with places like Delaware, Calumet, Negaunee, Twin Lakes, Ironwood, and especially Covington and Herman much more likely to see the earliest snowfall. Other years, Mohawk can get a surprise early dusting like back in 2009.