Bao the whole thing like a mummy using cling wrap. Rain and wind can find its way in easily.

Yes! Like luggage wrapping service. Thing with outdoor boxes the gasket/seals are waterproof from light splashes but not "thunderstorm waterproof", plus over time there's surely a little gap here and there and that's where the water gets in. I assume that all the wires go in from the bottom, leave the bottom loose so water can drain out, the goal is to prevent water from seeping in the top and sides.