A cold drop, or DANA, is a slow-moving, high-altitude mass of cold air that causes severe weather, including torrential rain and flash floods, when it encounters warm, moist air near the surface.
A cold drop, or DANA (Depresión Aislada en Niveles Altos), is not your typical storm. It is a complex meteorological phenomenon born high in the atmosphere, capable of unleashing some of the most intense and damaging rainfall events in Mediterranean regions.
The term DANA is the official scientific name, used by meteorologists to describe the atmospheric setup: an isolated low-pressure system that forms at high altitudes. The term cold drop is the more familiar phrase used by the public, often referring directly to the resulting violent weather—torrential rain, flooding, and destructive winds. In simple terms: DANA is the cause, and the cold drop is the effect.
At the center of a DANA’s creation is the polar jet stream—a fast-flowing, narrow corridor of air located 7 to 12 kilometers (4 to 7 miles) above the surface, in the upper troposphere. The jet stream is like an atmospheric conveyor belt, separating frigid polar air to the north from much warmer tropical air to the south. It undulates around the globe, creating meanders and bends that can sometimes deepen into large dips known as troughs.
When a trough deepens far enough, it can pinch off entirely, cutting loose a bubble of extremely cold air from the main current. This bubble is now isolated from the fast-moving flow, drifting slowly or remaining almost stationary. This is the moment a DANA is born—a high-altitude cold pool adrift above the Earth’s surface.
A DANA on its own is simply a pocket of cold air aloft. The true danger comes when it positions itself above a region saturated with warm, moist air at the surface. In the Mediterranean, this combination is most common in autumn, after months of summer heat have warmed the sea to bath-like temperatures.
Warm air, loaded with water vapor, is buoyant. It rises quickly through the atmosphere until it meets the much colder, denser air of the DANA. The temperature contrast is so stark that it creates extreme atmospheric instability—a recipe for violent upward motion. As the warm air rises, it cools and the moisture condenses into towering cumulonimbus clouds.
These clouds are capable of holding massive volumes of water. The DANA acts almost like a lid being lifted from a boiling pot—the heat and moisture surge upward, feeding rapid condensation, and releasing enormous amounts of energy. This is the engine of the intense thunderstorms and torrential rain associated with cold drops.
Unlike a fast-moving cold front, a DANA drifts slowly or can remain anchored over the same location for hours or even days. This stationary nature allows the same area to be pounded repeatedly by heavy rain, as moisture-laden air is continuously drawn into the towering storm clouds.
The result is often extraordinary rainfall totals in a very short time. In some cases, a single cold drop has delivered more precipitation in a few hours than the affected area would normally receive over several months. Because the rain is concentrated in such small areas, neighboring regions may remain almost dry, creating a dramatic contrast in weather conditions only a few kilometers apart.
When this much rain falls so quickly, the ground cannot absorb it. Streets turn into rivers within minutes, cars are swept away, and low-lying neighborhoods flood rapidly. Riverbanks burst, sending torrents into agricultural land and destroying crops. Steep slopes are especially vulnerable—water saturates the soil, causing landslides and mudflows that can bury roads and homes.
Infrastructure is often overwhelmed. Drainage systems clog, bridges collapse under the pressure of debris-filled water, and transportation grinds to a halt. In coastal towns, storm surges can combine with swollen rivers, creating a double threat of flooding from both directions. Power outages, communication failures, and damage to water treatment facilities compound the crisis.
Cold drops occur most often in September and October, though they can happen at other times of year if the right conditions align. The Mediterranean Basin is particularly prone because of its geography: a warm inland sea surrounded by mountainous terrain, which funnels moist air upward into the cold air above.
The duration of a cold drop can range from a single day of intense storms to a multi-day event that leaves entire regions cut off by floodwaters. The longer the DANA stays in place, the greater the damage it can cause.
While many cold drop events have caused significant damage, two stand out in recent Spanish history for their sheer intensity and tragic impact. They serve as a stark reminder of the destructive power of these weather events.
The cold drop of September 2019 was, at the time, one of the most devastating on record. It struck southeastern Spain, causing catastrophic flooding in the regions of Valencia, Murcia, and Andalusia. The storm resulted in seven deaths and an estimated €2 billion in damages. In some areas, over 300 mm (nearly 12 inches) of rain fell in just 24 hours, overwhelming riverbeds and turning streets into torrents. This event demonstrated how quickly a DANA could unleash a year's worth of rain, leaving a trail of destruction in its wake.
Just five years later, Spain was hit by a cold drop of even greater magnitude. Beginning on October 29, 2024, an exceptionally powerful DANA brought unprecedented rainfall to the Valencia region and other parts of eastern Spain.
This event became the deadliest natural disaster in Spain's modern history, causing over 200 deaths and widespread devastation. In some locations, like the town of Chiva, nearly 500 mm (20 inches) of rain fell in just eight hours.
The intense downpour caused rivers and ravines to overflow, sweeping away cars, destroying homes, and overwhelming critical infrastructure. This tragedy highlighted not only the destructive power of a cold drop but also the increased severity of these events, which scientists attribute to the effects of climate change on sea surface temperatures.
While cold drops cannot be prevented, understanding their formation helps forecasters issue warnings in advance. Meteorologists track the jet stream and sea surface temperatures to anticipate when and where a DANA might form. Public awareness is equally important—knowing that a forecast of “isolated heavy rain” in autumn could mean the arrival of a DANA can prompt timely preparations, from securing property to avoiding flood-prone areas.
Cold drops are a reminder that weather is not just about temperature and sunshine. It is a dynamic, interconnected system where events high above the Earth’s surface can have life-changing consequences on the ground.
Published:
August 15, 2025
Was this helpful?
Alternate names:
Subscribe to our Newsletter