I was driving to work this Wednesday morning and was lucky enough to see a few breaks of sunshine mixing in with the clouds. At the same time, we also had rain showers off in the distance. But through this busy atmosphere, I could see a faint view of a rainbow.

This led me to be somewhat optimistic about the weather, but that optimism went away pretty quickly as the remainder of the day was rather gloomy. Rainbows do not happen very often, so it is worth explaining how and why a rainbow develops.

What are the optimal ingredients to be able to see a rainbow? First, ideally you want an open area where you can see the horizon very clearly and there is some rain falling in the distance. Second, the angle of sunlight is very important with the sun being at a maximum of 42 degrees above the horizon (or less). The way to remember this is that your shadow should be no longer than your height. Next, the rainbow will be appearing opposite of the sun. So you should have the sun at your back with the rain in front of you. 

And remember, the larger the raindrops, the better view of the rainbow. As that visible light from the sun reaches the raindrop, it will bend and refract the light. This is similar to what happens in a prism.

There are also fog bows, snow bows, and even moon bows. Very unusual optics in the atmosphere, but maybe it will give you some optimism about our weather.