It the container isn’t air tight and it can’t get wet it should be fine. I store my bales in a wooden blanket box. I sealed around the lid with door seals to prevent bugs getting in but then I also drilled holes and inserted small air vents in three of the sides so that the hay could still breathe and wouldn’t sweat, it’s more likely to sweat in plastic containers which then leads to mould, but out of sunlight it should be ok, depends how fresh the hay is too.