Some might like the winter atmosphere of a black/pagan themed metal festival, but I'm completely neutral and would support it and attend no matter when it's held.
When trying to entice perspective travelers, January in Minnesota is a tough sell. I'm obviously just guessing, but I would suspect a more mild month would draw more travelers.
I say stick with the month of Jan! The weather suits it perfectly and shit, I'll come up with any excuse to get off of work to attend it! Screw fall, COLD HARSH WINTERERER
I suggest any weekend other than the 3rd weekend of January (as it has been so far), which is also always the same weekend as the annual NAMM trade show in Anaheim, CA (National Association of Music Merchants) which is attended by lots of metal musicians and people who work in the music gear/instrument industry, etc...
I think the overall 'mood' of January fits the theme of the HC. How about the 2nd weekend of January (around the 15th)?