I have a similar problem (3d printer in a garage in a rainy city).

My solution was a drybox, which consists of:

Plastic storage bin with rubber gasket, mounted on it's side (lid facing forward) on a rack above the printer.

Reel rack similar to this installed in bin:

Teflon tube pokes through sealed holes in the box to guide the filament to the extruder

Then I put a paper lunch bag half full of drierite desiccant in the box.

Measured humidity outside the box is 63% inside the box it's 3%

Once the humidity in the box goes over 10%, which takes weeks, I replace the dririte with some fresh stuff. You can dry out the desiccant by cooking it in an oven at 425F for a few hours, been using the same jar of drierite for years now.