I live in LA (hot dry climate) and my house has a central swamp cooler, it was 115 F the other day and the thing worked great!
I have a travel trailer I like to use off grid, I also sometimes leave my dog in it for a few hours at a time, so I need it to stay cool for her.
The "5 gallon bucket swamp cooler" is not my idea, give it a quick Google to check out other designs.
I believe it originates from the burning man festival?
Anyways, this is my take on it.
Part of how my design differs / is improved is that I got a little float switch to run along with the tiny 12v water pump. This way, I can leave it running and when it runs out of water it will keep the fan on but shut off the water pump so as not to damage it.
I kept the inlet holes way towards the top to allow for a larger water reservoir.
I opted for a 12v plug is car fan instead of computer fans for increased air flow. But that made it larger because I had to make a shroud out of coroplast that is attached to the top of the bucket lid.
I used a lot of hot glue with a dual temp gun.
I improved the simplicity of the water dispersement system. After I had found the proper size hose for my pump I was having a hard time finding a "T" for it. I realized it wasn't necessary. I cut little holes in the last section of hose, blocked the end with hot glue, and cut it to size so that it spirals a few times going up but not too much more than needed.
I have it set in a ventilated bathroom (closet size) and stick the outlet out the door into the living space, in an attempt to suck dry air in through the bathroom window and direct cool air out into the living space and out the far window.