In the news
On 29 October, torrential rain affected several regions in eastern Spain, causing flash floods, particularly in the Valencia region. Spain has been facing severe flooding, the worst in decades, with at least 217 fatalities reported, primarily in Valencia. The central government deployed over 10,000 troops and police officers to assist with rescue and relief operations. Concerns remain that the casualty may increase, as rescue teams have access to previously isolated areas. 

On 30 October, Spain's national meteorological office, Aemet, reported that on the 29th of October, parts of Valencia, including the towns of Turis, and Chiva or Bunol, recorded more than 400 millimetres of rainfall within eight hours. It started with a storm with extraordinary rainfall, particularly in Chiva, where an eight-hour deluge exceeded the previous 20 months of rainfall. Floodwaters inundated the Magro and Turia river basins and overflowed the Poyo riverbed, submerging roads, railways, homes, and businesses. 

Issues at large
First, the delayed warnings. Spain's national meteorological office (Aemet) had issued warnings during the initial days of the rain. However, Valencia’s regional authorities delayed sending text alerts by about 12 hours on the day of the storm, when floodwaters were already surging. When they warned residents to seek shelter, many people were exposed to rising water levels, and trapped in vehicles or underground garages. This delay provoked public criticism over the tardiness of alerts and the perceived slow response of emergency services. Further rains are predicted in the region, which has compounded the challenges for emergency responders.

Second, a brief note on DANA. The primary reason for the floods in Valencia has been the destructive weather phenomenon known as the Depresión Aislada en Niveles Altos (DANA) or a high-altitude isolated depression. This phenomenon usually occurs when cold air from higher altitudes moves over the warm waters of the Mediterranean Sea. This temperature variation creates instability, with the colder air at higher altitudes sitting over warmer and moist air near the surface. It creates rapid upward movement of warm air, forming dense rain clouds. These clouds can remain stationary over an area for extended periods, resulting in intense and prolonged downpours. 

In this instance, DANA was aggravated by such a low-pressure storm system. The storm effectively became "trapped" over Valencia, unable to move due to the high atmospheric pressure surrounding it. Thus, it resulted in torrential rains over a relatively small area. Many climate experts link this instability to the record-high temperatures of the Mediterranean Sea. 

Third, the vulnerability of the region. Eastern and southern Spain, in particular, are vulnerable to similar extreme weather events because of their geographic location, where warm and humid air from the Mediterranean meets cooler Atlantic fronts, often in mountainous regions. Autumn rainfall is common in this part of Spain, and floods have occurred in recent years, especially during this time of the year. 
 
In perspective
First, frequent extreme weather events in Spain. Spain has endured climate extremes in recent years, with a severe drought in the northeastern region. The dry heat has also hardened the soil surface, thereby water runs off rather than being absorbed, increasing the frequency of floods.

Second, climate change and its links to similar extreme weather events. Climate change has escalated DANA’s frequency and impact. Warmer seas generate more heat and moisture resulting in larger and more powerful storms. Along with these heightened factors, climate scientists warn that as the Mediterranean continues to warm, the region can expect more frequent and intense storms, accentuating the broader influence of climate change on weather patterns and extreme events. Such floods highlight the need to enhance early warning systems to swiftly get people out of harm’s way.