42º Above – How to Find a Rainbow

Rain Henderson

Florida summers create a patchwork quilt of rainbows, sewn together by sun showers and longer days. Around 5 o’clock the sweltering heat waves battle the sudden burst of the clouds creating, what seems to be, the perfect canvas for a rainbow. But why haven’t I seen one?

A rainbow isn’t really a “thing”, it’s an optical phenomenon. Light enters a water droplet, slowing down and bending as it goes from air to denser water. The light reflects off the inside of the droplet, separating into its component wavelengths–or colors. When light exits the droplet, it makes a rainbow…but there’s more to the recipe.

Rainbows are only visible if the sun is less than 42º above the horizon. I don’t know about you but I don’t walk around with a protractor in my pocket, maybe I should start. A quick way to estimate the sun’s angle in relation to the horizon is by looking at your shadow. If it’s length is longer than your actual height, no rainbows will be seen. For a more specific, trustworthy estimate I hopped on suncalc.org to get the numbers. Today in Jacksonville, at 9:56am the sun was about to hit 42º above the horizon, so if it had been raining in the right spot you could’ve seen a rainbow somewhere between sunrise and 10pm. Later today, the sun will begin to descend and around 6pm it will begin to lower under 42º, making those 5 o’clock sun showers useless to us rainbow hunters. The higher the sun is (within the 42º angle, of course) the lower and flatter the rainbows will be. Unfortunately for us working and living downtown, the horizon is blocked by empty architecture and glassed skyscrapers meaning we won’t see that rainbow at exactly 42º above the horizon but more likely closer to sunset, 7pm-8pm. 

So the basics: if it’s raining before 10am or after 6pm look in the opposite direction of the sun and you might just catch a glimpse of a world wonder. Happy hunting!