Being stuck inside with young children on cold wet days is hard on both children and parents. There are many fun educational things that you can do that use everyday materials you have around the house at very little cost.
Try stepping back when your kids complain about feeling bored. This will empower them to think for themselves and learn to be resilient. It will also encourage them to find their own way out of the boredom, and the problem-solving process helps them feel good about themselves.