Last week, beachgoers off an Iranian island were met by an eerie sight. The sand turned bright red as if the shoreline was painted in blood. The phenomenon on Hormuz Island was captured in viral videos amassing tens of millions of views, showing torrential rain washing crimson soil from the island’s mountains into the ocean.

The scene is just surreal and it’s due to the island’s unique geology.

What’s Behind “Blood Rain”?

“In the case of blood rain, strong winds or storms can whip up dust and sand,” explains the UK Met Office. “As this becomes airborne, it can get caught up in atmospheric circulation, where it can be carried for thousands of miles. Eventually, the dust will either fall out of the sky due to gravity or will be caught up in rain clouds, where it mixes with the water droplets. When these fall as rain, the raindrops could appear red.”

In Hormuz, however, the red hue isn’t from dust carried by wind — it’s from the island’s own soil. 

Hormuz Island is often called the “Rainbow Island” for its multicolored mineral deposits, rich in iron oxide (aka rust). It is this compound that gives the soil in the area its distinctive red hue. When heavy rains fall, they wash this iron-rich soil from the mountains into the sea. As the minerals mix with the seawater, the shoreline turns deep red. Besides iron oxide, there are also layers of clay, carbonates, shale, and iron-rich volcanic rocks that have created a kaleidoscope of colors, from deep reds to vibrant yellows and oranges.

“Heavy rain today, red beach,” wrote an Iranian tour guide on Instagram, sharing footage of the striking transformation. The videos show floodwater cascading down rocky slopes, carrying with it the island’s signature red soil.

Elsewhere, in places like Kerala, India, red rain was linked to airborne spores and dust.

Hormuz Island locals and entrepreneurs have learned to leverage the “blood rain” phenomenon. Hormuz Island has become a must-see destination for curious travelers. Visitors flock to the island to witness the rare event, which often coincides with heavy rainfall. The sight of red waves crashing against the shore, set against the backdrop of the island’s colorful mountains, is nothing short of mesmerizing.