Most of the outdoor cat houses out there are not very good when it comes to being completely waterproof. There are a lot of them that feature water-resistant construction, but none of them are truly able to keep the water out.
In case of rainy weather, fabric construction cat houses will become soaked, no matter how water-resistant they are. One of the best water-resistant cat houses is the CozyCatFurniture Waterproof Insulated Cedar Outdoor Cat House for Winter and Summer, but you will really have to splurge on it.
If you decide to buy another cat house, you can still go for it. Just make sure that you keep it in a partially covered area to offer your cat a bit of protection against snow and rain.