I don't fancy the "breathing moisture in" theory due to the sheer volume. I can agree with the concept, just not the amount. But how? Could the rain and wind have been heavy enough to directly drive the water upward, past the threads? I know we're not supposed to tighten the lid so it's left loose, and given enough time and direct rain and ground splash, combined with swirling wind I'll speculate that's what happened. (Note to self: carry second trashbag.)

One Bearikade plus--a gasket seal. (I own both FWIW).

Cheers,
_________________________
--Rick