St. Patrick's Day Starts Rainbow Season!

March 17, 2021
Double Rainbow in Iowa

It’s time to celebrate being Irish (or pseudo-Irish) and look for that pot of gold waiting for you at the end of the rainbow. I can’t help you with the Irish gig, but let’s celebrate the start of rainbow season with fun facts about rainbows and why we associate rainbows with St. Patrick’s Day.

This is the season to start seeing rainbows, whether you are in Ireland or Texas. But before we get into the magic of how rainbows are made, how exactly did rainbows, pots of gold, and leprechauns become Irish folklore?

Irish Lore and Leprechauns

According to folklore: If you catch a leprechaun, you can force him to tell you where he hid his pot of gold, which is somewhere at the end of a rainbow. 

An 1888 book on Irish legends and tales, Irish Wonders, has the first known reference to a “pot of gold.” As the tale goes, Tim O’Donovan of Kerry captured a leprechaun and forced him to disclose the spot where the ” pot o’ goold ” was concealed. The leprechaun claimed he had no spade but staked the location with his hat. The next morning, Tim was tricked because there were stakes in every direction!

Now a leprechaun in Irish lore was not the cheery, bright-eyed fellow from the Lucky Charms cereal cartoons. He was a small, old, withered fairy who lived alone and mended the shoes of Irish fairies. He was known to be a little cranky and not the most popular fairy. Like many of the “little people,” he possessed treasures and tended to hoard his gold. Because these treasures could not be found, this tale that grew into legends that pots of gold were found at the end of the rainbow. Because you can never find the “end” of a rainbow, you can’t get the pot of gold (unless you catch the leprechaun).

St. Patrick and Rainbows

In Christianity, the rainbow is featured in Genesis when God destroy the earth with a flood due to his disappointment in humans and corruption. He promised never to do so again. (Genesis 9:13–17).

I do set my bow in the cloud, and it shall be for a token of a covenant between me and the earth. And it shall come to pass, when I bring a cloud over the earth, that the bow shall be seen in the cloud: And I will remember my covenant, which is between me and you and every living creature of all flesh; and the waters shall no more become a flood to destroy all flesh. And the bow shall be in the cloud; and I will look upon it, that I may remember the everlasting covenant between God and every living creature of all flesh that is upon the earth. And God said unto Noah, This is the token of the covenant, which I have established between me and all flesh that is upon the earth.

St. Patrick was a Christian saint who preached God’s word in a country transitioning from paganism. St. Patrick viewed the rainbow as a representation of God’s promise to never again destroy the earth with a flood. So, the Irish myths and legends of rainbows and pots of gold merged with Christian beliefs to where we are today! The fabric of history is a fascinating tapestry, isn’t it?

How Are Rainbows Formed?

So, let’s talk about the magic of rainbows! 

In the spring, the heated air from the South is expanding north and mixing with the cold air remaining from winter. This produces those spring storms! And the combination of raindrops and sunlight produces our beautiful, multi-colored rainbows!
six rainbows

Mix water droplets, sunlight, and you get a rainbow—or, in this case six rainbows. SOURCE: The Astrophysics Science Division of NASA/GFSC Credit Terje O. Nordvik

How do the colors form? As the sunlight pours into the rain, each drop acts as a prism, refracting the light. The white sunlight is broken down into its component colors. The back of the raindrop reflects this series of colors, each at a different angle. You see different colors from different raindrops and it blends into a bow.

Each raindrop acts as a prism Source − Wikipedia.

How Are Double Rainbows Made?

For double rainbows, light entering raindrops refract twice, going in from the air to the water and reflecting back out of the water into the air. Each refraction produces a rainbow. You can frequently see the bright first rainbow with a fainter reverse rainbow on the outside.

Once you know the basic science, you can start to understand why there are so many different crazy rainbows. The more the light bounces around, reflecting and refracting, the more different rainbows you can get. 

There are even multiple rainbows. Rain, mist, reflections and light bouncing through the water droplets creates many different rainbows. One scientist, with a laser, created 200 at once.

Ever heard of monochrome rainbows? Sometimes, at sunrise or sunset, when the blues and greens have faded from the sky, you get a brilliant all-red rainbow.

An un-enhanced photo of a red (monochrome) rainbow. Source − Wikipedia.

Can the End of a Rainbow Be Reached?

The end of a rainbow is beyond our reach, retreating as we go toward it. It forms when light shines through specific water droplets and, through refraction and reflection, separates into colors that emerge at different angles. No two people can see the same rainbow, because they can not be in the same place; each will see color rays that come from different water droplets.

In addition, a rainbow is actually a complete circle (with its center opposite the Sun), but is often cut off by the horizon (passengers in planes may sometimes see a complete circle). All that being said, there are those who attest to having reached a rainbow’s end; although these people did not find a pot of gold, they did discover a rare and special experience.

Where is the Best Place to Look for a Rainbow?

To see a rainbow, three conditions must be met: 1. raindrops, 2. the sun is shining, 3. the observer is between the sun and the rain.

The best time to see a rainbow is during spring weather conditions when there are alternating showers and clear skies.

Near sunset, look in the area of the sky directly opposite the setting sun.

Getting The Pot of Gold

Whether there are one or fifty rainbows, they are all beautiful images that retreat as you approach them. But, here’s some hope for St. Patrick’s day. A number of European countries have rainbow folklore, spinning tales of elusive gold. In Silesia (part of Central Europe), legend says that angels put a pot of gold at the end of the rainbow and only a naked man can reach it.

So fortify yourself with green beer, warn the neighbors, and go for the gold!

About This Blog

Mike Steinberg is Senior Vice President for Special Initiatives at AccuWeather Inc in State College, Pennsylvania. He is also a member of the National Weather Association and the Canadian Meteorological and Oceanographic Society.

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