I don’t know how to stop it getting so wet in there…
Can you see where it’s coming in from? Like maybe from the side walls where it connects to the bottom of the floor, possibly seeping in.
If it’s entering from the roof you could try to put some thick plastic over it and secure it.
I put a tarp over the top to waterproof it. So I guess it’s coming in the gap for the door
Maybe attach a dog door to the entry?
Looks like the hole is to big. Cats don’t need a hole that big. It’s not a dog
Put in a cat flap
And you cut it all the way down so the rain is running in too
Well, if it is seeping in between the floor and the side walls, then you could run a bead of weatherproof caulking around the outside of it.
Post a picture of the outside of your cat Haven.
If that’s your cat, how about letting inside your house!!? WTF!
Condensation?
How about a flab of scrap fabric stapled to the inside of the opening?
Have you tried using silicone caulk to seal the seams? There’s also a number of spray paint type products that will coat and presumably seal the sprayed areas. (Spray might be easier to apply.) Something called maybe Plasti-coat or flexi-seal or something like that? Also they make a peelable primer spray paint for vehicles. If it’s peelable, it might help seal any small cracks or gaps if applied in multiple thick coats. Hope that helps! So sweet of you to care for kitty
Cats like to go outside and can’t always be let back inside because people go to work or sleep. This gives them somewhere to take shelter and get food if they require it. It’s not for them to live in.
Build a tunnel around the doorway like an igloo
I would leave like a flappy door
Beautiful cat, though!