Complex sentence: 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.
Split into simpler sentences: 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.