WEATHER is an important element in any setting, providing sensory texture and contributing to the mood the writer wishes to create in a scene. With a deft touch, weather can enhance the character's emotional response to a specific location, it can add conflict, and it can also (lightly) foreshadow coming events.
However, caution must accompany this entry: the weather should not be used as a window into a character's soul. The weather can add invisible pressure for the character, it can layer the SCENE with symbolism, it can carefully hint at the internal landscape, but it must never OVERTLY TELL emotion. Such a heavy-handed approach results in weather cliches and melodrama (a storm raging above a bloody battle, a broken-hearted girl crying in the rain).
Sight: A multi-colored arch, sometimes bright and clear, sometimes faint and fuzzy. Rainbows can vary in size, from single and double ones that cross the sky, to smaller ones around waterfalls or even beneath the spray of a sprinkler.
Mood: Rainbows in the sky aren't something you see everyday, so the sight of one is like a gift. This is why some people feel happy, optimistic, or even lucky after seeing one. Rainbows usually occur after a rainfall, when the weather clears. Such a sight may remind viewers of a new beginning or a fresh start.
Symbolism: God's promise, diversity, gay pride, happiness
Possible Cliches: rainbows as signs of good luck, rainbows at the conclusion of a story to signify a happy ending, leprechauns and pots of gold
OTHER: The rainbow is basically what happens when water meets light; the light is spread out into its spectrum of colors so the observer can see it. Rain or some form of water (mist, a fountain, a waterfall, etc.) must be present, and the sun should be behind the observer when facing the phenomenon. When we see a rainbow, we are seeing the place where light and water meet. We can't see the water that is below the horizon, which is why the rainbow's arch always seems to stop there. The higher we are above the ground, the more the rainbow can be seen, as evidenced in this picture of a rainbow taken from an airplane. No clue why that would be relevant to anyone's story, but it sure is cool.
Don't be afraid to use the weather to add contrast. Unusual pairings, especially when drawing attention to the Character's emotions, is a powerful trigger for tension. Consider how the bleak mood of a character is even more noticeable as morning sunlight dances across the crystals of fresh snow on the walk to work. Or how the feeling of betrayal is so much more poignant on a hot summer day. Likewise, success or joy can be hampered by a cutting wind or drizzling sleet, foreshadowing conflict to come.