Re: humidity when reloading
If you are reloading indoors, you should be OK. It is not good practice to store powder in damp humid places, but simply reloading when it's raining outside should not cause issues.
Concrete scientific evidence: I have a M70 that shoots like crap. I once loaded up a box to feed it during a torrential downpour. The gun still shot like crap with that ammo. No discernible change from reloading during rain.