Bra makers say that the bra cannot be used under rainy conditions. A wet bra
will grow mold that will damage your paint.

I use mine only under dry conditions. If it rains, or is about to rain, I
remove the bra. If it gets wet, I remove and dry it before returning it to
the van. If I'm traveling and it begins to rain, I stop and remove the bra.

I think a bra is probably not going to be of much use in your area with so
much rain.