The ceremony will take place on October 29 in Valencia's City of Arts and Sciences complex, a year to the day after muddy torrents killed 236 people and wrecked infrastructure.

The extent of the damage in the eastern Valencia region prompted widespread outrage at the authorities' management of the disaster and a blame game between the politically opposed central and regional governments.

Scientists say human-driven climate change is intensifying extreme weather events such as the torrential rain behind last year's floods.

The catastrophic situation was further fuelled by a rapidly warming Mediterranean Sea.

Oceans have absorbed 90 percent of the excess heat produced by human activity since the dawn of the industrial age, according to scientists.

After a summer of ferocious wildfires that burned a record amount of territory in Spain, Prime Minister Pedro Sanchez has proposed a national pact against climate change.

"Having wildfires of this magnitude, having (storms) like the ones we experience in autumn and winter, shows that the climate emergency affecting the world is accelerating and worsening, especially on the Iberian Peninsula," Sanchez said when announcing the pact.