Weather has long been a favorite topic of conversation, from unseasonably hot, sunny days to skin-soaking drizzle that seems to last for weeks. But some weather really is worth talking about. These are the moonbows that shimmer in the night sky, the haloes, spots and dots deflected from the sun's rays, and the clouds that look like spaceships. Here's a selection of some of the most amazing weather phenomena, from the Northern Lights to frost flowers.