A powerful cloudburst in the high-altitude villages of Dharali in Uttarakhand’s Uttarkashi district caused devastating flash floods on Tuesday, leaving at least four people dead and over 50 missing. Local residents said the cloudburst occurred in the catchment area of the Kheer Ganga river, resulting in a sudden and forceful release of water that damaged or washed away many houses.

According to initial reports, around 10–12 people could be buried under the debris, and about 20–25 hotels and homestays might have been swept away in the floods. Rescue teams have been deployed, but ongoing rainfall and difficult terrain are making search efforts extremely challenging.

What is a cloudburst?

A cloudburst is an extreme weather event. It happens when intense rain falls suddenly over a small area

typically 100 millimetres (10 centimetres) or more of rain in less than an hour over about 20 to 30 square kilometres.

This kind of heavy rain can cause flash floods, landslides, and serious damage to infrastructure, especially in mountainous regions like the Himalayas.

Cloudbursts are common in hilly areas where warm, moist air is forced upwards along mountain slopes. This process, known as orographic lifting, causes the air to cool and condense quickly. When the clouds can't hold any more moisture, they release it suddenly in the form of a heavy downpour.

Inside thunderclouds, strong upward air currents can keep raindrops suspended longer, allowing them to grow larger. This is known as the Langmuir precipitation mechanism. When these upward currents suddenly weaken, all the water falls at once, leading to a cloudburst.

Cloudbursts can also occur when warm air meets cooler air, which causes sudden condensation. During the monsoon season in India, winds carrying moisture from the Bay of Bengal or Arabian Sea rise as they hit the Himalayan slopes, increasing the chance of cloudbursts.

The amount of water involved is huge. Just 100 millimetres of rain over one square metre equals 100 litres of water. When this happens across a mountain area, billions of litres of water can fall in minutes, flooding rivers and villages.

Because cloudbursts are sudden and localised, they are very hard to predict, making early warnings difficult. Their impact can be deadly, especially in vulnerable mountain communities.

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