Flash floods in Spain this week have turned village streets into rivers, ruined homes, disrupted transportation and killed at least 95 people in the worst natural disaster to hit the European nation in recent memory.

Rainstorms that started Tuesday and continued on Wednesday caused flooding across southern and eastern parts of the country, stretching from Malaga to Valencia.

Valencia alone recorded a death toll of 92 after receiving what Spain's weather service said was more rain in eight hours than it had received in the last 20 months.

But are torrential downpours just another act of nature — unavoidable and inevitable?

Scientists say a warming planet is at play, and extreme weather events are occurring more frequently and in much greater strength than ever before.

What's behind the deadly floods?

Spain's flash floods were caused by a destructive weather system in which cold and warm air meet and produce powerful rain clouds, a pattern believed to be becoming more prevalent due to climate change.

The phenomenon is known locally as DANA, a Spanish acronym for high-altitude isolated depression, and unlike common storms or squalls it can form independently of polar or subtropical jet streams.

When cold air blows over warm Mediterranean waters it causes hotter air to rise quickly and form dense, water-laden clouds that can remain over the same area for many hours, raising their destructive potential. 

The event sometimes provokes large hail storms and tornadoes as seen this week, according to meteorologists.

Eastern and southern Spain are particularly susceptible to the phenomenon due to its position between the Atlantic Ocean and the Mediterranean Sea. Warm, humid air masses and cold fronts meet in a region where mountains favour the formation of storm clouds and rainfall.

This week's DANA was one of the three most intense such storms in the last century in the Valencia region, Ruben del Campo, spokesperson for the national weather agency Aemet, said.

"Forecasts were in line with what happened. But in an area between Utiel and Chiva, in the province of Valencia, rainfall exceeded 300 litres per square metre," Mr del Campo said.

"In that area, storm systems formed and regenerated continuously."

'Fingerprints of climate change'

While experts say it will take time to analyse all the data to determine if this particular DANA was caused by climate change, most agree that an increase in temperature of the Mediterranean and warmer and more humid atmospheric conditions contribute to producing more frequent extreme episodes.

"We're going to see more of these flash floods in the future. This has the fingerprints of climate change on it, these terribly heavy rainfalls, and these devastating floods," Hannah Cloke, professor of hydrology at the University of Reading, told Reuters.

Professor Cloke said even early warnings of heavy rain based on reliable forecasts did little to prevent the fatalities and people needed to understand the real danger.

"Just telling people that it's going to rain quite a lot, it's not good enough … we could see that people were putting themselves at risk driving in floodwaters, and there was just so much water that it has overwhelmed these places."

Before the term DANA was coined in the early 2000s, any heavy rainfall in the autumn, characteristic of the Mediterranean climate, used to go by the popular name "gota fria" (cold drop) in Spain and parts of France. The term is still widely used colloquially.

Its origin dates back to 1886 when German scientists introduced the idea of "kaltlufttropfen", or cold air drop, to describe high altitude disturbance but without apparent reflection on the surface.

Aemet says the concept of cold drop is outdated and defines DANA as a closed high-altitude depression that has become isolated and separated from an associated jet stream. The agency says DANAs sometimes become stationary or even move backwards, from east to west.

Flooding in Central Europe last month after a severe four-day rainfall was found to have been twice as likely due to climate change by the World Weather Attribution service.

Their study also found global warming increased the intensity of rains by 10 per cent, as well as their duration.

The UN Environment Programme describes the Mediterranean as "a climate change hotspot where vulnerabilities are exacerbated", with the basin warming 20 per cent faster than the global average.

The Mediterranean, which includes coastal regions of 22 countries in Europe, west Asia, and north Africa and is home to about 480 million people, also bore record-high heat in the 2024 summer period.

"Since the early 1980s, the Mediterranean Sea has been warming at approximately 0.4°C per decade, which is faster than the global ocean average. This warming is leading to more frequent and severe marine heatwaves, especially in the last 20 years," CMCC researcher Giulia Bonino said.

When was Spain's last major natural disaster?

The death toll, which includes three people in other regions, appeared to be the worst in Europe from flooding since 2021 when at least 185 people died in Germany. 

Spain has experienced similar autumn storms in recent years, though nothing compared to the devastation over the last two days, which recalls floods in Germany and Belgium in 2021 in which 230 people were killed.

It is possibly the nation's worst in its modern history as the number of victims surpassed 87 people killed in a 1996 flood near the town of Biescas in the Pyrenees mountains.

In 1957, dozens of people died in floods in the city of Valencia which led to the construction of a new course of the Turia river to prevent floods in the city centre.

"Events of this type, which used to occur many decades apart, are now becoming more frequent and their destructive capacity is greater," said Ernesto Rodriguez Camino, a member of the Spanish Meteorological Society.

Emergency services fear the number of victims could rise in the coming days while rescue operations remain underway.

Casualties have so far been reported in the Valencia, Castilla La Mancha, and Andalusia regions, however transport disruptions have been impacted as far as Barcelona and the capital Madrid.

Spain’s government declared three days of mourning starting on Thursday.

The floods come as the country is still recovering from a severe and prolonged drought this year, which has made it more difficult for the land to absorb high volumes of water.

ABC/Reuters/AP