I think there's a reason Paavo has the summer to itself. Not good marathoning weather once you get away from Lake Superior (and often not all that great weather up in Hurley to be honest).
Same goes for the winter months. I would think a November marathon would work, though it would be a roll of the dice. Maybe EC or LC would consider switching from May to November if they struggle with their current dates. That still leaves a crowded May schedule, though.