You might be able to hook the meter up to your battery and pull one fuse at a time and see where the problem is if you have an understanding of that kind of thing. Assuming the short is on the other side of the fuse block.
Two people it can go pretty quick.
It could be wet tail or headlights or a bad brake light switch. Those are easy to check first.
Battery should read 12.6v. 2.1v per cell. Anything higher is probably surface charge. Turn on lights for for a bit to drain it then test again and you should have 12.6v. As far as a drain I use an amp probe and start pulling fuses. Keep in mind you may have a module or two on that could read a draw. Being in wet conditions water in an electrical connector could be your problem. I’ve seen water in ABS module connector cause a draw.