Free: Contests & Raffles.
Rain isn't going to hurt it, but putting it in a plastic garbage bag will.
I'm no expert but if you want some soured to the bone meat go ahead and garbage bag it. Then, put it against your back while you are hiking out and working up a good sweat.
Think of it like this....you cook a nice steak...it comes off the grill.....you put it on a plate with some foil....it gets hotter right. For your game meat the goal is the opposite....cooling it down is number one...especially with bear...all that fat and grease...you want to let it cool and get air, not trap all the heat in.