# dry rainbow

**URL:** <https://boards.straightdope.com/t/dry-rainbow/119644>\
**Category:** Factual Questions\
**Created:** [July 18, 2002, 4:38pm UTC](https://boards.straightdope.com/t/dry-rainbow/119644 "2002-07-18T16:38:06Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![vanilla](https://avatars.discourse-cdn.com/v4/letter/v/f19dbf/32.png) [@vanilla](https://boards.straightdope.com/u/vanilla)\
**Post date:** [July 18, 2002, 4:38pm UTC](https://boards.straightdope.com/t/dry-rainbow/119644/1 "2002-07-18T16:38:06Z")

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Has anyone ever seen one?  
me and my son were in a bus last week. there were a few cirrus clouds up in the sky.  
I looked at one, adn there was a pretty pastel rainbow.  
No rain anywhere!  
It was neat.  
How is that possible?

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**Author:** ![Hanna](https://avatars.discourse-cdn.com/v4/letter/h/b3f665/32.png) [@Hanna](https://boards.straightdope.com/u/Hanna)\
**Post date:** [July 18, 2002, 4:58pm UTC](https://boards.straightdope.com/t/dry-rainbow/119644/2 "2002-07-18T16:58:13Z")

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Maybe it is like my experience with[rain with clear skies?](http://boards.straightdope.com/sdmb/showthread.php?s=&threadid=124843)

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**Author:** ![Philster](https://avatars.discourse-cdn.com/v4/letter/p/13edae/32.png) [@Philster](https://boards.straightdope.com/u/Philster)\
**Post date:** [July 18, 2002, 4:58pm UTC](https://boards.straightdope.com/t/dry-rainbow/119644/3 "2002-07-18T16:58:24Z")

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rain???

Isn’t the key ingredient airborne water vapor…which doesn’t have to be precipitation in the form of rain?

Enough water droplets to scatter light, but not enough to cause noticable precipitation could lead to a rainbow.

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**Author:** ![bbeaty](https://avatars.discourse-cdn.com/v4/letter/b/c0e974/32.png) [@bbeaty](https://boards.straightdope.com/u/bbeaty)\
**Post date:** [July 18, 2002, 9:56pm UTC](https://boards.straightdope.com/t/dry-rainbow/119644/4 "2002-07-18T21:56:59Z")

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Was it up in the cirrus clouds? Was it NOT a “bow”, but just a patch of rainbow colors? If so, you were seeing a “sundog” which was caused by refraction within ice crystals. Usually there are two “sundogs”, one on either side of the sun.

UIUC: meteorology: light & optics: ice crystals  
[http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/opt/ice/sd.rxml](http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/opt/ice/sd.rxml)

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**Author:** ![vanilla](https://avatars.discourse-cdn.com/v4/letter/v/f19dbf/32.png) [@vanilla](https://boards.straightdope.com/u/vanilla)\
**Post date:** [July 18, 2002, 10:18pm UTC](https://boards.straightdope.com/t/dry-rainbow/119644/5 "2002-07-18T22:18:26Z")

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Yes! it was just a patch of bow only on the cloud.