Then, when it says 'When the seas and mountains fall. In dreams they will see their loved ones again.
But when everything seems hopeless, in dreams there is still hope. 'We will walk in bitter rain' is ash from mount doom or other parts of Mordor. The fellowship sets out in winter, so that's why it says 'When the cold of winter comes' 'Starless night will cover day' as Sauron's power grows the shadow spreads across the land, covering the face of the sun.
