When the sun gets closer to the horizon, the atmosphere is thicker and so the light from the sun has lost more blue color from all the extra scattering, so it even looks more red than when it is higher up. Yes, rainbows may form at night with the moon replacing the sun. When this occurs, it is called a moonbow. It is as far and as near as the water droplets themselves. The chirping of a cricket has been shown to provide a rather close indication of the air temperature.
Lightning takes the shortest path.