The cooling of a system will only be as good as the air drawn in to it. Hot humid air is going to cause multiple problems with a system and in these conditions liquid cooling may be a better avenue to pursue. Ideally keep the system out of direct sunlight and also not in a cupboard or other enclosed area. If is it preferred for the system to be hidden away ensure the spacing is adequate for good external air flow, and there is a way to get fresh air into the space.

Generally just having a vent is not going to remove the amount of heat a performance PC is going to produce and getting some small USB fans to run is better than nothing. Ideally though, as with the system itself, you will need a fan to draw air into the spacing, and another to push air out. These should be aligned with the system as best as possible so air drawn into the enclosed space is directed towards the front of the case, and the fan pushing air out is assisting removing the heated air coming out if the PC.