Here he is referencing short lived sexual affairs that his wife, Lady Chatterly, has had with other men; he is inferring that these affairs, like the snows of yesteryear, are ephemeral and once gone leave nothing tangible behind.
His wife has had with other men. Here he is referencing short lived sexual affairs this. His wife is Lady Chatterly. These affairs are ephemeral and once gone leave nothing tangible behind. This was like the snows of yesteryear. This is what he is inferring.