The best way is to carry out the necessary processing of the tilt angle of the air conditioning indoor and outdoor units through the hole in the wall, so that the lower side of the hole in the wall from the inside to the outside of the lower height, so that it is tilted; so that even if there is rain into the hole in the wall, the rain will automatically flow to the outdoors, and will not flow into the indoor.

At the same time, you can add a small rain cover above the mouth of the outer wall of the hole in the wall to prevent the rain from drifting directly into the hole in the wall.