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.

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Reel rack similar to this installed in bin:
HATCHBOX-2-Spool-3D-Printer-Filament-Tabletop-Wall-Mount-Rack-0-0.jpg

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.