I have seen it close to six feet and had to have two extensions on the auger and start drilling standing on the tailgate of my truck. It has been awhile since I have seen it that thick, but if this -50 keeps up we might see it again.
Dude, you're a better man than I am, I once drilled a dry hole on Big Lake at around 4 1/2 feet. I quit there tho! I had even augered out around the top of the hole so's I could sink the powerhead down a ways, so I reckon around 5 feet, could'a been six tho, I never struck water! And you're right, this bloody weather probably put another foot or more on, and I was cutting 34" last week. And on top of it all, most of my winter fishing is darkhouse spearing for pike, and cutting a 2'x3'x3+' hole gets damn interesting without some type of explosive