Blood rain
Rain that appears red, often caused by dust or microalgae in the water
No single value: Blood rain is a material, and its colour varies. The background shows its family, red.
Blood rain is a rare event where rainwater appears red, sometimes startling those who see it. The colour is now known to come from airborne red dust or spores of microalgae, though in the past it was thought to be real blood and seen as a bad omen. Reports of blood rain go back to ancient times and have occurred in many countries.
- Blood rain has been recorded since at least the 8th century BC.
- Modern science links it to red dust or microalgae spores in rainwater.
- Kerala, India, saw notable blood rain events in 2001 and 2012.
- In the past, it was widely seen as a bad omen.
- Recent studies traced Kerala's red rain algae to Austria.
What colour is Blood rain?
Blood rain is when rainwater falls with a red or reddish tint, making it look as if blood is coming from the sky. This rare event can last from a few minutes to several days and usually affects small areas. The red colour stands out most against pale backgrounds and has startled people for centuries.
Where does Blood rain come from?
The name 'blood rain' comes from the belief, common before the 17th century, that the rain was actual blood. Ancient texts like the Iliad mention it as a sign from the gods. Over time, people realised it was not blood but something that made the rain appear red. Modern science has shown that the colour comes from dust or microalgae spores in the rainwater.
How is Blood rain made?
Today, scientists know that blood rain is usually caused by either red dust or spores of green microalgae called Trentepohlia annulata. The dust can be blown by winds from distant places, while the algae spores can travel in clouds across continents. When these particles mix with rain, they give the water a red appearance.
What Blood rain means
In many cultures, blood rain was seen as a warning or bad omen. Ancient Greeks and Romans, as well as medieval Europeans, often took it as a sign of coming disaster, war, or death. In literature and chronicles, it was used to foreshadow tragic events or show the power of the gods.
Red around the world
What the red family means from country to country.
The flag is red, white and red. Legend says Duke Leopold V's white tunic was soaked in blood at the siege of Acre, all but the band under his belt.
Politics and protestCourageSource: Flag of AustriaRed is the colour of the Social Democrats. Coalitions are named by party colours: red, yellow and green make a "traffic light", and black, yellow and green a "Jamaica" coalition.
Politics and protestSource: Political colourThe flag is red and yellow, the rojigualda. The colours were chosen for the navy in 1785 because they stood out at sea, and the men's football team is called La Roja.
Politics and protestPrideSource: Flag of SpainIn the last part of a bullfight the matador uses a small red cape, the muleta. Bulls do not see red as we do. It is the movement that draws them, and the colour hides the blood.
Danger and warningCourageSource: BullfightingAt the San Fermin festival in Pamplona each July, runners and crowds dress in white with a red neckerchief and red sash.
Festival and celebrationJoySource: Festival of San FermínMany Hindu brides marry in a red sari or lehenga. In much of north India a married woman wears sindoor, a red powder, along the parting of her hair.
Weddings and marriageLuck and prosperityJoyLoveSource: SindoorShades and relatives of Blood rain
Some reports of blood rain may actually describe red aurorae or other red-coloured weather events. The phenomenon can be confused with rain coloured by other substances, but true blood rain is linked to red dust or microalgae. The intensity and shade of red can vary depending on the amount and type of particles present.
Questions people ask about Blood rain
What colour is blood rain?
Blood rain appears red or reddish, making rainwater look as if it is stained with blood. The shade can vary depending on the amount and type of particles in the rain.
Where does the name 'blood rain' come from?
The name comes from the old belief that the rain was actual blood falling from the sky. This idea was common before the 17th century, especially in Europe and the Mediterranean.
What causes blood rain?
Blood rain is caused by red dust or spores of microalgae, such as Trentepohlia annulata, suspended in rainwater. These particles can be carried long distances by wind and clouds.
Where has blood rain been reported?
Blood rain has been reported in many places, including India (Kerala), Italy (Sicily, Rome), Spain (Canary Islands, Malaga, Seville), Austria, Germany, and Sri Lanka.
Was blood rain always understood as a natural event?
No. For centuries, people thought it was a supernatural sign or real blood, often seen as a warning of disaster. Only in the last few centuries have natural explanations become accepted.
Good reading and sources
- BBC News | SOUTH ASIABBC, Article
- Unravelling the ‘blood rain’ mysteryThe Hindu, Article
- Red rain could prove that aliens have landedThe Guardian, Article
- Blood rain on WikipediaEncyclopedia
- More pictures on Wikimedia CommonsPictures
- Wikidata recordOpen data
The facts on this page come from the Wikipedia article "Blood rain", written by its contributors and used under the CC BY-SA 4.0 licence, and from its Wikidata record (CC0). Rang rewrote the text in its own words, with AI assistance, and compares every page with the article to make sure no passage is copied. It may be reused under the same CC BY-SA 4.0 licence with a link back.
It may contain mistakes. The swatch is an approximation: named colours are not fixed standards, and every screen shows them a little differently. If something is wrong, tell us. Last refreshed 2026-10-03.
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