After I thawed the padlock in winter at least three times with hot water in the morning, when the kids (and I) needed their bikes, I thought it would be a good idea to keep the padlock reasonably dry using a cover. After the cover was finished it stopped freezing, so I wait until next year whether it really keeps it from freezing in. It hasn't been dripping wet since I installed the cover, though. 

The cover is fixed at the flap of the hasp, it can swiveled to the top to get to the padlock. After the padlock is open, it just stays at the flap when the hasp is opened.

The model consists of three parts, to be able to modify each part without having to print everything again. 

All parts are printed with TPU (Filatech Filaflex40), 0.2 mm layer height, 50% infill (as far as I can remember, for details see the files), they can't be assembled when made of a rigid material like PETG or PLA.

The fixed part of the hinge is put on the flap of the hasp. 

Then the other part of the hinge is slid into it. This part has a dove tail, which is pushed into the cover. The cover has a hole, where the bolt of the this part of the hinge fits in, to keep it from falling apart.