Why were the floods in Spain so bad? A Visual Guide | Spain

AAt least 140 people have died in Spain after torrential rains unleashed the country's deadliest floods in decades, unleashing a torrent of muddy water that turned village streets into rivers, destroyed homes and washed away bridges, railway tracks and cars.

An unknown number of people remain missing, while thousands of others are without electricity or telephone access. Most of the fatalities were in the coastal region of Valencia, where nearly a year's worth of rain fell in just eight hours, according to the state agency.

Deaths were also reported in the Castile-La Mancha region and the Andalusian province of Málaga.

This before and after slider shows the dramatic change in the landscape south of Valencia:

More than 400 liters of rain per square meter fell on Tuesday in the most affected areas. Rubén del Campo, a spokesman for Spain's meteorological agency, told El País: “A relatively strong storm, a heavy downpour like we see in spring or summer, can be 40 or 50 liters per square meter.” That practically multiplies it by that Tenfold.”

The heavy rain was attributed to a phenomenon known as Gotta friaor “cold drop,” which occurs when cold air flows over the warm waters of the Mediterranean. This causes atmospheric instability as the warm, moist air rises quickly to form towering, dense clouds that can dump heavy rain.

The clouds can remain over the same area for hours, multiplying their destructive potential and, as seen in Spain this week, triggering violent hailstorms and tornadoes along with rain.

In recent years, scientists have warned that Mediterranean waters are warming rapidly, rising up to 5°C above normal. Because hot air can hold more moisture, the risk of catastrophic rainfall increases.

“There is no doubt that these explosive downpours have been exacerbated by climate change,” said Dr. Friederike Otto, head of global weather attribution at the Center for Environmental Policy at Imperial College London.

As three days of national mourning begin in Spain and rescue workers begin searching devastated areas, questions are emerging as to why the alert urging people to stay in their homes was only sent out after the flooding began.

The state weather agency AEMET issued a red alert for the Valencia region on Tuesday morning and kept it active as conditions worsened throughout the day.

But it took until after 8 p.m. for civil protection to send out a warning asking residents not to leave the house.

One man told the news site Eldiario.es that the alarm came when he was already trapped in his car and the water was up to his chest. “Shortly after 8pm, after I was up to my neck in water and swallowing mud, the alarm went off,” he said.