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What is the rarest type of rain?

Rain comes in many forms, from light drizzles to heavy downpours. While common types of rain like showers and thunderstorms occur frequently around the world, some extremely rare and unusual rains exist.

Overview of Rare Rain Types

Some of the rarest types of rain include:

  • Red rain
  • Black rain
  • Yellow rain
  • Green rain
  • Blood rain
  • Animal rain

These strange rains are caused by a variety of factors, from meteorological phenomena to volcanoes and algae blooms. They typically occur in very isolated, localized areas and only last for a short period of time. Historical accounts of these bizarre rains date back centuries, though scientific documentation is limited.

Red Rain

Red rain is a rare meteorological phenomenon in which rain falls with a distinct red coloration. The red color is caused by atmospheric dust or particulate matter that mixes with rainwater. Several notable cases of red rain have been reported over the years:

  • In 1818, red rain fell over the Maldive Islands in the Indian Ocean for nearly two weeks. The cause remains unexplained.
  • In 2001, red rain fell sporadically over the southern Indian state of Kerala over a period of two months. Initial theories suggested the colored particles were extraterrestrial in origin, but later evidence indicated it was most likely airborne spores from locally prolific algae.
  • In 2012, scientists collected red rain samples during an incident in Sri Lanka. Spectroscopic analysis revealed the presence of microscopic algae cells which likely originated from local algae blooms.

While the exact cause often varies, these red rains seem to occur most frequently in tropical coastal areas where phytoplankton and dinoflagellate algae populations can rapidly bloom to high densities. When winds blow, these lightweight algae become aerosolized and later return to earth as a dusting of red particles mixed with rain.

Black Rain

Black rain occurs when rainwater becomes contaminated with pollutants, turning it dark in color. The pollutants that cause black rain include:

  • Volcanic ash – Rain can turn black when volcanic eruptions or ash plumes release volcanic ash into the atmosphere. The ash then mixes with raindrops.
  • Factory smoke or urban pollution – In industrial areas or urban centers with high air pollution, black particles and soot can collect in clouds and then wash out as black rain.
  • Oil rain – Spills of crude oil or petroleum from damaged tankers, rigs, or refineries can be picked up by rain, resulting in oil rain.
  • Wildfire soot – Smoke and charred particulate matter from wildfires or biomass burning results in dark black rain when incorporated into precipitation.

Historic cases of black rain linked to volcanic eruptions include the raining of black ash following the 1883 Krakatoa eruption and the 1902 eruption of Mount Pelee on Martinique. More recently, oil rain occurred in Louisiana in the aftermath of the 2010 Deepwater Horizon oil spill catastrophe.

Yellow Rain

Yellow rain is an unusual phenomenon in which rain falls with a bright yellow coloration. Two main mechanisms can cause yellow rain:

  • Pollen rain – In some areas, seasonal rainfall can wash tons of pollen grains from trees and plants into the air. Accumulations of pollen particles can stain rainwater a yellow or golden hue.
  • Chemical agents – In Southeast Asia in the 1970s and 80s, numerous reports emerged of yellow rain allegedly containing toxic chemicals. However, the yellow color was later attributed to naturally occurring bee feces picking up chemical dyes from vegetation.

In the United States, oak pollen rain occurring in spring months can make raindrops appear yellow across oak-dominant forests of the Southeast and Midwest. Pine pollen rain also creates yellow rainfalls in the pine forests of the South. These pollen rains are short-lived, clearing up as soon as the rainy weather ends.

Alleged Chemical Weapon Attacks

In the late 1970s, refugees fleeing civil conflict in Laos described ongoing attacks using “yellow rain”, an oily liquid that fell from the sky, causing painful blisters and even death on contact. Similar reports emerged from Cambodia around the same time. The U.S. government accused Soviet-allied Vietnam and Laos of using experimental chemical weapons, triggering an international scandal.

Later scientific analysis showed the yellow rain was most likely bee feces contaminated with plant-derived dyes. The toxins reported were naturally occurring in bee droppings. While no chemical weapons were found, the “yellow rain” reports drew global attention to the humanitarian crises unfolding in Southeast Asia.

Green Rain

Green-colored rain is primarily caused by two natural phenomena:

  • Comet dust – When Earth passes through the dust tail of a comet, the fine green particles called nickel-iron sulfides in the tail can tint rainwater green.
  • Algae populations – Blooms of green algae in the ocean can release particles that seed rain clouds, causing green rainfall similar to red rain.

One of the earliest documented cases of green rain occurred in Kerala, India from July 25-September 23, 1896. The rain was traced to a comet called Comet 189 II, which had passed close to Earth and left a dense trail of evaporated particles.

In 2013, algal blooms off the coast of Sardinia caused sporadic green rain to fall over the Mediterranean island. Samples showed the rainwater was dense with single-celled green algae of the species Pleurochloris comosa.

Blood Rain

“Blood rain” is a disturbing phenomenon in which blood-colored rain falls from the sky. Though not actual blood, it is caused by:

  • Red dust particles – Windblown red dust from desert regions or drought-stricken lands can mix with rain, causing it to appear blood-like.
  • Microorganisms – Certain algae and microorganisms in clouds can stain rain red when they burst and release pigments.

One of the most famous cases of blood rain happened in southern Spain in 1901, when rain colored by fine red dust from the Sahara Desert fell over wide areas. Microscopic analysis of the rain showed it contained red coccolithophore algae. Saharan dust rains still occur regularly in Spain.

Another bloody rain event took place in India in 2001, fascinating locals and scientists. Chemical analysis found the rain was colored by airborne spores from locally common green algae and lichen.

Animal Rain

Among the strangest types of rain are those containing live animals or animal remains. Though extremely rare, these disturbing animal rains result from:

  • Waterspouts – Powerful waterspouts or tornadoes over water can lift animals like fish or frogs into the air and carry them distances before raining them down.
  • Strong winds – Extreme winds can occasionally loft light animals like spiders into the air, to later fall with precipitation.

Historic reports of animal rain include:

  • In 1881, ranchers in California reported rain consisting of live pollywogs, the juvenile form of frogs and toads.
  • A 1947 incident in Marksville, Louisiana allegedly included heavy rain containing live four-inch crabs.
  • In 1959 in Sicily, a light rain contained detached leaves, branches, and various animal remains.
  • More recently in 2005, small fish were reported raining down on the city of Vijayawada, India after a severe thunderstorm.

While animal rain reports are often disbelieved or misreported, the phenomena highlights the ability of extreme weather to occasionally carry creatures skyward to surprising locales.

What Causes Rare Types of Rain?

These odd rain types are caused by:

  • Unusual particles in the atmosphere – Dust, chemicals, pollen, volcanic ash, and even microorganisms can enter the atmosphere and seed rainclouds.
  • Algae blooms releasing pigments – Rapid algae reproduction leads to airborne particles that dissolve to color rain.
  • Pollution particles – Soot, oil droplets, and industrial particulates contaminate clouds.
  • Strong updraft winds – Tornadoes, waterspouts, and hurricanes can lift animals into rainfall.

In most cases, the unusual rain is highly localized and only lasts a short time before dissipating or drying up. The rarity of these events results from the unique combinations of geography, weather, and substances that must come together to produce colored or contaminated rain.

Where Do Rare Rains Occur?

Unusual rain types tend to appear most in:

  • Tropical coastal areas prone to algae blooms
  • Desert and arid regions producing windblown dusts
  • Polluted industrial areas
  • Volcanically active regions
  • Areas frequently struck by waterspouts and tornadoes

However, they can unpredictably appear anywhere in the world given the right conditions. For example, vortex rains likely require strong thunderstorms to loft animals aloft, while algae blooms releasing colored pigments depend on factors like water temperature, salinity, and nutrient levels.

Geographic Examples

  • Saharan dust rains often appear in Spain and the Mediterranean.
  • Southeast Asia’s tropical coastal climates witnessed multiple colored rains.
  • The Midwest and Southeast U.S. see occasional oak pollen rains.
  • Waterspouts over the Great Lakes have sucked up and rained fish.

Are Rare Rains Dangerous?

Most types of odd rain are harmless, but some can pose health hazards:

  • Red, yellow and black rains – Often harmless but can reduce visibility for driving.
  • Acid rains – Uncommon rainfall more acidic than normal due to pollution, potentially harming ecosystems.
  • Chemical agent rains – Alleged chemical weapon releases like yellow rain reportedly caused blisters and skin irritation.
  • Animal rains – Dropped animals like fish or frogs are generally already dead or injured.

The main threat comes from air pollution contaminants in rainfall. Consumption or exposure to black, yellow or chemical rains could theoretically cause sickness, though little evidence confirms this. The other odd rain types are mostly just bizarre nuisances.

Notable Historic Events of Rare Rains

Some key events involving unusual rain types include:

Year Location Details
1824 Kerry, Ireland Red rain fell for a week attributed to Saharan dust clouds.
1825 Genoa, Italy Red rain containing yellow, blue, and green particles fell for eight days.
1883 Krakatoa, Indonesia Black rain fell for weeks after the enormous volcano eruption.
1896 Kerala, India Green rain fell for two months, linked to the Comet 189 II passing.
1901 Southern Spain Saharan dust rain turned bloody red across wide areas.
1970s-80s Southeast Asia Multiple alleged yellow rain chemical weapon attacks reported.

Recent Examples and Documentation

Despite being rare and ephemeral, modern cases demonstrate these unusual rains still sporadically occur:

  • In 2013, a brief green rain in Sardinia, Italy was well-documented by residents and scientifically sampled as algae rain.
  • During Hurricane Irma in 2017, light red algae rain was reported and filmed falling in Naples, Florida.
  • In 2019, black rain fell across regions of Russia following explosive wildfires, caused by soot particles.
  • As recently as 2020, there are still occasional reports of black and yellow rain linked to pollution in urban parts of India.

YouTube videos exist claiming to show recent animal rain occurrences, though these lack definitive verification. Most modern examples are shared rapidly on social media when they occur in populated areas.

Factors Leading to Increased Documentation

Several factors make documentation and analysis of unusual rains more common today than in historical times:

  • Public awareness and interest in reporting rare events
  • Cell phone cameras allow documentation and sharing of photos/videos
  • Advances in chemical analysis techniques to identify rainwater contaminants
  • Atmospheric modeling and tracking of dust clouds or pollution transport
  • Media dissemination and news coverage of uncommon weather

Whereas in the past, an unusual rain would often only be noted through hearsay, today’s technology allows increased scientific study and public knowledge when these fleeting events occur.


While most rain consists of standard water droplets, nature can sometimes conjure up brief, exotic rainfalls filled with color, debris, or even animals. These rare rain types form under specific environmental and weather conditions that transport unusual particles aloft. Though often called “blood rain” or “red rain”, the coloring agents are usually harmless minerals, pollutants, or microorganisms. While fascinating anomalies, these special rains are typically localized blips on the meteorological radar.