Why is it difficult to indicate during a blizzard whether the train is moving or not?

For an observer inside the train, some kind of motionless body is required in order to understand whether the train is moving or not. Such a body can be a train station platform, trees, houses, etc. If there is a blizzard outside the window, then it is difficult to understand whether the train is moving or not, you have to draw conclusions only by the sound of the wheels, but by the shaking of the car.