What Is Blood Rain?

blood rain red rain

Although blood rain lacks any actual blood content, its mere presence has perpetually evoked fear within human hearts. Throughout history, this phenomenon, often referred to as “red rain,” has frequently been construed as an ominous omen, portending impending calamity. Among the earliest documented references to red rain, a historical relic harking back to 191 BCE surfaces in the annals of the Roman historian Livy.

The manifestation of blood rain roused such disquietude within the Roman Senate that it prompted a decisive course of action—consuls offering sacrifices of fully grown individuals to the deities they deemed appropriate. In 1348, Germany bore witness to a crimson downpour, an occurrence swiftly woven into the fabric of superstitious interpretations as an augury of the dreaded Black Death.

However, the passage of time has heralded a transformation in perception. Over the centuries, these arcane beliefs have yielded ground to a more enlightened comprehension of the authentic nature underlying blood rain, unraveling its true mechanisms and origins.

Among the earliest documented references to red rain, a historical relic harking back to 191 BCE surfaces in the annals of the Roman historian Livy. Ancient scholars and writers also mention them, such as Homer in the “Iliad” (lines 52–54 of Book XI and line 459 of Book XVI), Plutarch, and medieval ones like Al-Ghazen. There is a mention of a similar phenomenon in the Bible (Exodus 7:19). The most famous rains of this kind fell in:

  • 1803, February – in Italy;
  • 1813, February – in Calabria;
  • 1838, April – in Algeria;
  • 1842, March – in Greece;
  • 1852, March – in Lyon;
  • 1869, March – in Sicily;
  • 1870, February – in Rome;
  • 1887, June – in Fontainebleau.

Blood rains are observed outside of Europe as well, for example, on the islands of Cape Verde, at the Cape of Good Hope, and so on. Blood rains occur due to the admixture of red dust with ordinary rain, consisting of the tiniest organisms of red color. The homeland of this dust is Africa, where it is lifted to a great height by strong winds and carried to Europe by upper air currents. Hence its other name, “trade wind dust.” Because of this dust, the air in the middle part of the Atlantic Ocean often becomes so dark that this part was called the “Dark Sea” by the ancient Greeks and Romans. Comprehensive research on red rains was conducted by Erenberg, who collected numerous pieces of documentary evidence from the 16th century BCE (including from 461 BCE in Roman writings) to the last quarter of the 19th century. In 1849, he published the monograph “Trade Wind Dust and Blood Rain” (German: “Passat-Staub und Blut-Regen”).

The Cause of the Blood Rains

Baghdad blood rain
Baghdad, red (blood) rain. Image: The Sun.

Blood rain, a meteorological phenomenon, boasts a diverse range of triggers, with the prevailing contemporary cause arising from the interaction between Saharan desert dust and storm-laden clouds. This intricate interplay involves rain or snow, a shroud of dust, and a dynamic storm system, collectively orchestrating the genesis of the enigmatic red rain. The key to the manifestation of tinted raindrops lies in their passage through a sub-cloud dust cluster situated beneath the canopy of clouds.

The spectral hue of the ensuing rain emerges as a testament to the iron oxide content nestled within the dust particles. The richness of the crimson or russet hue hinges on the density of iron oxide, a factor that governs whether the rain assumes a ruddy or tawny demeanor. While this striking precipitation can transiently imbue surfaces with a reddish tint, prolonged exposure might eventually erode this chromatic flourish, gradually rinsing away the dust particles.

The geographic distribution of Saharan dust-imbued blood rain unfolds on the stage in a choreographed manner according to the whims of the wind and atmospheric conditions. However, the epicenter of this captivating phenomenon predominantly graces the landscapes of Europe. Southern European enclaves in proximity to the Sahara Desert’s outstretched reaches, notably Spain and southern France, bear witness to the most frequent occurrences. In contrast, the United Kingdom, tucked away in its corner of the world, experiences these striking episodes several times within a year’s time.

Other Causes of Blood Rain

Pollution and Blood Rain

In the year 2018, the industrial hub of Norilsk, situated in Siberia, found itself enshrouded in an eerie phenomenon: red rain. A surreal ambiance descended upon the town as vehicles assumed crimson hues and blood-like water pooled upon the asphalt, casting a somber pall over the locale. Yet the genesis of Norilsk’s red rain diverged from the norm. Unlike the familiar red dust borne by the winds from the Sahara Desert, the culprit here was of human creation.

Russian industrial city of Norilsk hit with 'bloody' red rain
Russian industrial city of Norilsk hit with ‘bloody’ red rain. Image: Rbth.

A symphony of potent winds bore aloft a substantial volume of untreated iron oxide, commonly recognized as rust, from the Nornickel metallurgical plant. This airborne residue was the red hue that cascaded over the city. When this iron oxide combined with raindrops suspended in the atmosphere and subsequently descended as precipitation, a distinctly unnatural rainstorm materialized—a rainstorm of artificial blood, so to speak.

Microscopic Organisms

Beyond the realm of colored dust, an intriguing biological underpinning unveils another facet of the enigmatic red rain phenomenon. The annals of red rain history bear witness to two instances in which biology, rather than mineral composition, played the role of the chromatic catalyst.

2001 kerala blood rain
2001, red rain (blood rain) in Kerala state. Image: Vocal.media.

In the annals of 2001, the Indian state of Kerala found itself shrouded in a continuous crimson deluge, an extraordinary meteorological theater that spanned a two-month interlude. With each raindrop, cities and landscapes were transiently drenched in hues of red, an event that seemed to defy both explanation and expectation. At first, the scientific gaze turned toward the familiar Sahara dust analogy, invoking a narrative reminiscent of the European tableau. Yet, meticulous scrutiny revealed a bewildering revelation—the particles descending from the heavens were, in fact, living entities.

Stranger still, these entities bore no genetic fingerprint, perplexing scientists and evoking extraordinary theories. Among these conjectures stood a provocative hypothesis—were these peculiar organisms the offspring of extraterrestrial lineage, borne to Earth by the explosive embrace of an asteroid? A thunderous detonation that heralded the rain’s arrival lent credence to this cosmic narrative.

However, the tale took an unexpected twist. Careful analysis unraveled the enigma, revealing that the fallen entities were none other than spores—silent travelers on the winds. Cloaked under the scientific nomenclature of Trentepohlia annulata, these airborne wanderers belonged to the realm of stratospheric spores, inhabitants of lofty atmospheric domains. Storm clouds acted as unwitting vessels, carrying them earthward and precipitating a swift multiplication that conferred the heavens’ scarlet hue upon terrestrial landscapes.

Haematococcus pluvialis (Haematococcus pluvialis), in differential interference contrast
Haematococcus pluvialis (Haematococcus pluvialis), in differential interference contrast.

Akin to a mysterious sequel, the Spanish city of Zamora bore witness to a kindred event in 2014, wherein the streets flowed with crimson rain once more. This time, the orchestrator was Haematococcus pluvialis, a green freshwater organism. Yet the riddle persisted—whence came these alien travelers? Not native to the region nor known to inhabit proximate water sources, the origins of these spores remained shrouded in mystery, an enduring testament to nature’s artistry and capacity for wonder.


  • Tatlock, John S. P. (October 1914), “Some Mediaeval Cases of Blood-Rain”, Classical Philology, The University of Chicago Press, 9 (4): 442–447, doi:10.1086/359914
  • Christian Gottfried Ehrenberg. Passat-Staub und Blut-Regen. — Berlin, 1849.