Costa Rica's Strange Skies and Natural Mysteries

Introduction

Costa Rica’s strange skies are a good example of how ordinary natural processes can produce extraordinary-looking experiences. Across the country, people have reported rainbow-coloured clouds, glowing skies, unusual flashes and lights associated with earthquakes or volcanic activity. Some sightings have entered mystery culture because they appeared sudden, vivid and difficult to explain at first glance. Yet many have plausible natural mechanisms, while others remain interesting historical reports rather than solved cases.[The Weather Channel]weather.comThe Weather ChannelCosta Ricans Stunned By Rare Iridescent 'Rainbow' Cloud | The Weather ChannelSeptember 21, 2015…Published: September 21, 2015

The appeal of these events lies in the gap between what people see and what they can immediately identify. A bright shape above a mountain, a red glow from a crater or a flash before an earthquake can look otherworldly when experienced without instruments or scientific context. Costa Rica’s active geology, tropical atmosphere and dramatic landscapes provide plenty of opportunities for such encounters, making unusual lights part of the country’s wider tradition of strange but often explainable phenomena.

Iridescent clouds and unusual skies

One of Costa Rica’s most memorable modern sky events occurred in September 2015, when a vivid “rainbow cloud” appeared over parts of the country, including areas around San José. Images spread rapidly online because the cloud seemed to contain a flowing spectrum of colours unlike a normal rainbow. Some observers interpreted the sight in symbolic or spiritual terms, while meteorologists identified it as cloud iridescence, a known optical effect.[The Weather Channel]weather.comThe Weather ChannelCosta Ricans Stunned By Rare Iridescent 'Rainbow' Cloud | The Weather ChannelSeptember 21, 2015…Published: September 21, 2015

Cloud iridescence happens when sunlight passes through thin clouds containing very small water droplets or ice particles of similar size. Instead of producing a conventional rainbow, where light is separated by raindrops into a broad arc, these tiny particles diffract light and create patches of pastel colours close to the Sun. The effect is usually short-lived because the cloud conditions must be unusually precise: the cloud needs to be thin, newly forming or structured in a way that allows the light waves to interact.[NOAA NESDIS]nesdis.noaa.govNOAA NESDISWhat Are Rainbow Clouds? | NESDIS | National Environmental Satellite, Data, and Information ServiceAugust 31, 2025…Published: August 31, 2025

The Costa Rican “rainbow cloud” became a useful example of how modern technology changes the life of a strange sighting. In earlier generations, a rare atmospheric display might have remained a local story. Smartphones and social media turned it into an international curiosity almost immediately, while also allowing experts to identify the mechanism behind the spectacle. The mystery was not that the event was fake, but that a genuine natural event looked unfamiliar enough to invite unusual interpretations.

Similar confusion can occur with other atmospheric effects. Bright halos around the Sun or Moon, unusual cloud shapes and dramatic sunset colours may be mistaken for signs of something unusual in the sky. In a country with volcanoes, mountains and humid tropical weather systems, changing light conditions can create striking scenes that are visually strange without requiring an extraordinary explanation.

Earthquake lights and luminous reports

Costa Rica’s geology provides another source of unusual light reports. The country sits in a highly active tectonic region, and stories of flashes, glows and strange sounds connected with seismic activity have long circulated. A 2024 study by Costa Rican researchers examined 13 historical narratives involving possible earthquake-related light and sound phenomena, comparing them with international research on earthquake lights. The authors suggested that some traditional accounts may preserve observations connected with seismic events, while also stressing their value as historical narratives rather than straightforward scientific measurements.[revistas.una.ac.cr]revistas.una.ac.crof Possible Evidence about Historical Tectonic Activity in Costa Rica | Revista Geográfica de América Central…

Earthquake lights are among the more debated natural mysteries in geophysics. Reports from around the world describe glowing bands, flashes, coloured lights or luminous clouds before, during or after earthquakes. Scientists have proposed several possible mechanisms, including electrical effects created when stressed rocks generate charges that move through the ground and interact with the atmosphere. Research has suggested that such reports are more common in certain geological settings, although the phenomenon remains difficult to study because earthquakes are unpredictable and the lights are rarely captured with reliable instruments.[National Geographic]nationalgeographic.comNational GeographicBizarre Earthquake Lights Finally Explained | National GeographicJanuary 7, 2014…Published: January 7, 2014

In Costa Rica, the challenge is separating possible earthquake-related phenomena from other sources of light. A flash in the sky during a tremor could be a genuine atmospheric or geological effect, but it could also be lightning, electrical infrastructure damage, a meteor, aircraft activity or a visual impression caused by the sudden movement of the ground. Historical accounts are valuable because they show what people experienced, but they rarely contain the measurements needed to identify the exact cause.

This uncertainty is what keeps earthquake lights within the territory of Forteana. They are not simply “unexplained lights” in the sense of lacking all possible explanations. Rather, they are reports where a real physical phenomenon may be involved, but where evidence is often incomplete and interpretation depends heavily on the circumstances of the sighting.

Volcanoes, glowing landscapes and mistaken mysteries

Costa Rica’s volcanoes create some of the country’s most dramatic natural displays. Places such as Poás Volcano have produced steaming craters, gas emissions, ash plumes and occasional glowing activity that can appear extraordinary to visitors. The volcano’s crater contains a hot, acidic lake and has experienced repeated eruptive episodes, including periods of increased activity monitored by scientists.[NASA Science]science.nasa.govScience Roiling Poás VolcanoNASA ScienceRoiling Poás Volcano - NASA ScienceMay 28, 2025…Published: May 28, 2025

Volcanic light is particularly powerful because it combines genuine danger, unfamiliar chemistry and visual drama. A red glow from a crater, a bright plume illuminated at night or glowing gases can easily become the basis for stories of strange lights. At Poás, scientists have documented episodes where intense heat and volcanic processes produced visible incandescence, showing how a natural geological process can resemble something mysterious from a distance.[Tico Times]ticotimes.netTico Times Poás Volcano Glows with Intense Heat as Night Hikes BeginTico TimesPoás Volcano Glows with Intense Heat as Night Hikes BeginAugust 4, 2025…Published: August 4, 2025

Volcanoes can also create misleading observations in other ways. Reflections from ash clouds, aircraft lights near mountain terrain, distant fires and unusual cloud illumination can all become difficult to judge in darkness. Costa Rica’s mountainous landscapes amplify these effects because a light source may appear suspended in the sky when it is actually near a ridge, crater or distant settlement.

The same principle applies to many reported “strange lights” across the country: the experience can be genuine even when the first interpretation is wrong. A witness may accurately describe what they saw while still lacking enough information to identify its source.

How natural events become mysteries

Strange lights gain cultural importance because they sit at the meeting point between observation and interpretation. A person seeing an unusual cloud or a glowing horizon is not necessarily reporting incorrectly; they are describing an event from a human perspective. The difficulty begins when appearance is mistaken for explanation.

Costa Rica’s unusual skies show several recurring patterns:

• Rare but real events: Iridescent clouds demonstrate how uncommon atmospheric conditions can create spectacular displays with a clear scientific explanation.[NOAA NESDIS]nesdis.noaa.govNOAA NESDISWhat Are Rainbow Clouds? | NESDIS | National Environmental Satellite, Data, and Information ServiceAugust 31, 2025…Published: August 31, 2025
• Natural processes with scientific debate: Earthquake lights remain a topic where reports exist, mechanisms have been proposed, and researchers continue to examine the evidence.[revistas.una.ac.cr]revistas.una.ac.crof Possible Evidence about Historical Tectonic Activity in Costa Rica | Revista Geográfica de América Central…
• Powerful landscapes creating powerful stories: Volcanoes, mountains and tropical weather make visual misidentification more likely while also producing genuinely dramatic sights.[NASA Science]science.nasa.govScience Roiling Poás VolcanoNASA ScienceRoiling Poás Volcano - NASA ScienceMay 28, 2025…Published: May 28, 2025

The lasting fascination of Costa Rica’s strange skies is therefore not simply that people have seen unusual things. It is that the country offers a rich setting where nature itself can appear mysterious. The most interesting cases are often those that begin with a simple question — “what was that light?” — and lead into a deeper look at geology, weather, perception and the ways communities remember unusual events.

Amazon book picks

Further Reading

Books and field guides related to Costa Rica's Strange Skies and Natural Mysteries. Use these as the next step if you want deeper reading beyond the article.

Book

The UFO Experience

By J. Allen Hynek

Directly relates to evaluating UFO evidence and sightings.

See on Amazon

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The Demon-Haunted World

By Carl Sagan

Fits natural explanations for strange observations.

See on Amazon

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Secret History of the World

By Jonathan Black

First published 2007. Subjects: Secret societies, History, World history, Secret societies -- History, Sociétés secrètes -- Histoire.

See on Amazon

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The weather book

By Williams, Jack

First published 1992. Subjects: Climate, Weather.

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Browse more on Amazon:The UFO ExperienceThe Demon Haunted WorldSecret History of the World

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Endnotes

1. Source: weather.com
Link:https://weather.com/news/news/costa-rica-rainbow-cloud

Published: September 21, 2015

2. Source: revistas.una.ac.cr
Link:https://www.revistas.una.ac.cr/index.php/geografica/article/view/18773

3. Source: nesdis.noaa.gov
Link:https://www.nesdis.noaa.gov/about/k-12-education/optical-phenomena/what-are-rainbow-clouds

Published: August 31, 2025

4. Source: science.nasa.gov
Title: Science Roiling Poás Volcano
Link:https://science.nasa.gov/earth/earth-observatory/roiling-poas-volcano-154358/

Published: May 28, 2025

5. Source: earthobservatory.nasa.gov
Title: During quiet periods, people as
Link:https://earthobservatory.nasa.gov/images/154358/roiling-poas-volcano

Published: March 5, 2025

6. Source: revistas.una.ac.cr
Link:https://www.revistas.una.ac.cr/index.php/geografica/article/view/14444

7. Source: weather.com
Title: HERE’S WHAT THEY SAW. By Sean Breslin•November 3,
Link:https://weather.com/news/news/iridescent-cloud-ocho-rios-jamaica

Published: November 3, 2015

8. Source: revistas.una.ac.cr
Link:https://www.revistas.una.ac.cr/index.php/geografica/article/view/18773/30330

9. Source: skybrary.aero
Title: Cloud Iridescence | SKYbrary Aviation Safety
Link:https://skybrary.aero/index.php/articles/cloud-iridescence

10. Source: nationalgeographic.com
Link:https://www.nationalgeographic.com/science/article/140106-earthquake-lights-earthquake-prediction-geology-science

Published: January 7, 2014

11. Source: ticotimes.net
Title: Tico Times Poás Volcano Glows with Intense Heat as Night Hikes Begin
Link:https://ticotimes.net/2025/08/04/poas-volcano-glows-with-intense-heat-as-night-hikes-begin

Published: August 4, 2025

12. Source: ticotimes.net
Title: Costa Rica Volcano Update: Poás Glows Red, Alerts Shift
Link:https://ticotimes.net/2025/06/04/costa-rica-volcano-update-poas-glows-red-alerts-shift

Published: June 4, 2025

13. Source: ticotimes.net
Title: Poás Volcano Crater Glows Red as Eruptions Persist
Link:https://ticotimes.net/2025/05/06/poas-volcano-crater-glows-red-as-eruptions-persist

Published: May 6, 2025

14. Source: ticotimes.net
Title: Costa Ricans Witness Meteor-Like Flash in Early Morning Sky
Link:https://ticotimes.net/2024/02/12/costa-ricans-witness-meteor-like-flash-in-early-morning-sky

Published: February 12, 2024

15. Source: nationalgeographic.com
Title: Earthquake lights facts and information | National Geographic
Link:https://www.nationalgeographic.com/environment/article/earthquake-lights

16. Source: sott.net
Title: Earthquake lights?
Link:https://www.sott.net/article/302065-Earthquake-lights-Mysterious-cloud-filmed-above-Costa-Rica

Published: September 16, 2015

17. Source: nationalgeographic.com
Title: By Brian Clark Howard Published
Link:https://www.nationalgeographic.com/science/article/150820-fire-rainbow-circumhorizontal-arcs-clouds-weather-science

Published: August 20, 2015

Additional References

18. Source: sott.net
Link:https://www.sott.net/article/315099-Disc-shaped-UFO-photographed-over-Irazu-volcano-in-Costa-Rica

Published: March 22, 2016

19. Source: teletica.com
Link:https://www.teletica.com/nacional/no-era-un-meteorito-objeto-que-ilumino-el-cielo-costarricense-tiene-origen-humano_406154

Published: April 1, 2026

20. Source: techtimes.com
Link:https://www.techtimes.com/articles/86451/20150919/rainbow-cloud-costa-rica-triggers-end-times-panic-scientists-scramble.htm

Published: September 19, 2015

21. Source: scielo.sa.cr
Link:https://www.scielo.sa.cr/scielo.php?lng=en&nrm=iso&pid=S2215-25632024000100455&script=sci_abstract

22. Source: scientificamerican.com
Link:https://www.scientificamerican.com/article/mysterious-light-associated-earthquakes/

Published: January 3, 2014

23. Source: dialnet.unirioja.es
Link:https://dialnet.unirioja.es/servlet/articulo?codigo=9353273

24. Source: everything.explained.today
Link:https://everything.explained.today/Earthquake_light/

25. Source: repositorio.una.ac.cr
Link:https://repositorio.una.ac.cr/items/cba9c22e-02ef-4074-ad68-17c9d6df07b2

26. Source: scielo.sa.cr
Link:https://www.scielo.sa.cr/scielo.php?pid=S2215-25632021000200030&script=sci_arttext

27. Source: nacion.com
Link:https://www.nacion.com/el-pais/reportan-avistamiento-de-posible-meteoro-que/ISBSFNPLWJATLHOAOVGXD67AHM/story/

Published: March 8, 2026