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What is double rain? Plain-English meaning
A double rain is a rainbow that appears with a second, fainter arc above the main one, caused by light reflecting twice inside raindrops.
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Definition
A double rain is a rainbow that appears with a second, fainter arc above the main one, caused by light reflecting twice inside raindrops.
Also seen as: double rainbow
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- September 8, 2026
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- Science & Nature
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Plain-English explanation
A rainbow forms when sunlight enters a raindrop, bends, reflects off the back of the drop, and then bends again as it exits, sending color back toward your eye. In a double rain, the light reflects twice inside the drop before returning, so the colors come out at a different angle. That creates a second arc above the first, but it is dimmer because some light is lost with each reflection. The secondary arc also has its colors reversed: red is on the inside, violet on the outside. You only see a double rain when the conditions are just right, with rain in one part of the sky and sunlight coming from behind you at a low angle.
Why it matters
Knowing what a double rain is helps you read the sky and understand why it looks different from a single rainbow. It also shows how light and water interact in the atmosphere, which is part of how weather and climate work. If you see one, you know that the light has taken a longer path through the raindrops, and that the second arc will be fainter and have reversed colors. That knowledge makes the experience more interesting and helps you explain it to others without relying on myths or vague ideas.
Concrete example
Imagine you are standing outside after a summer shower, with the sun low behind you and rain falling in the distance. You see a bright primary rainbow, and above it, a wider, fainter arc with the colors reversed. That is a double rain. The secondary arc is often so faint that you have to look carefully to see it, but on a clear day with steady rain, it can be visible for several minutes.
Often confused with
People often call any rainbow with a second arc a 'double rainbow' and think the second arc is just a reflection of the first. Actually, the secondary arc is a separate bow formed by light that reflects twice inside the raindrops, not a mirror image. Another common mix-up is thinking that the colors are the same in both bows, but they are reversed. The primary bow has red on the outside and violet on the inside; the secondary bow has violet on the outside and red on the inside.
Short definition: A double rain is a rainbow that appears with a second, fainter arc above the main one, caused by light reflecting twice inside raindrops.
Plain-English explanation
A rainbow forms when sunlight enters a raindrop, bends, reflects off the back of the drop, and then bends again as it exits, sending color back toward your eye. In a double rain, the light reflects twice inside the drop before returning, so the colors come out at a different angle. That creates a second arc above the first, but it is dimmer because some light is lost with each reflection. The secondary arc also has its colors reversed: red is on the inside, violet on the outside. You only see a double rain when the conditions are just right, with rain in one part of the sky and sunlight coming from behind you at a low angle.
Why it matters
Knowing what a double rain is helps you read the sky and understand why it looks different from a single rainbow. It also shows how light and water interact in the atmosphere, which is part of how weather and climate work. If you see one, you know that the light has taken a longer path through the raindrops, and that the second arc will be fainter and have reversed colors. That knowledge makes the experience more interesting and helps you explain it to others without relying on myths or vague ideas.
Concrete example
Imagine you are standing outside after a summer shower, with the sun low behind you and rain falling in the distance. You see a bright primary rainbow, and above it, a wider, fainter arc with the colors reversed. That is a double rain. The secondary arc is often so faint that you have to look carefully to see it, but on a clear day with steady rain, it can be visible for several minutes.
Common confusion
People often call any rainbow with a second arc a 'double rainbow' and think the second arc is just a reflection of the first. Actually, the secondary arc is a separate bow formed by light that reflects twice inside the raindrops, not a mirror image. Another common mix-up is thinking that the colors are the same in both bows, but they are reversed. The primary bow has red on the outside and violet on the inside; the secondary bow has violet on the outside and red on the inside.
Related terms
rainbow, primary rainbow, secondary rainbow, light refraction, raindrops
Practical tips
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More context
Double rainbows are caused by double reflection of sunlight inside raindrops, with the secondary bow having a larger radius. The secondary bow's colors are fainter because about 90% of light is lost at each internal reflection. The phenomenon is described in many cultures with symbolic meanings, but scientifically it is a purely optical effect.
Sources and further reading
- NOAA Ocean and Weather ResourcesNOAA explains oceans, ocean currents, tides, climate, weather forecasts, clouds, rain, snow, and wind patterns.