They don't seem to be going in with signs of WNS at all. Big Browns aren't as highly affected as Myotises, it seems, I guess because they're a far sturdier species than some Myotises, like the Little Brown. Likely, it's from having their hibernation disturbed by people, where this guy was, like an old building, as there aren't any caves near there. Honestly, though, the weather's been a bit off this year, not as bad as over a decade ago, but definitely enough to wake up a few sleepers. As for your area's weird weather, not sure where that is, but if insects are hatching and freezing, I don't doubt that a hibernaculum of bats somewhere woke up to a nasty surprise... Hibernation's a double-edge sword.