The European country is reeling from the October 29 disaster that has killed 227 people and sparked widespread fury at the governing class for their perceived mishandling of the crisis.

That outrage boiled over in the ground-zero town of Paiporta in the eastern Valencia region when King Felipe VI and Queen Letizia visited on November 3, in extraordinary scenes that stunned the world.

Furious residents chanting "murderers" pelted them with mud and projectiles as they struggled to wade through the crowds, while Prime Minister Pedro Sanchez was hastily evacuated.

The monarchs have since pledged to return to the Valencia region after another trip to the devastated town of Chiva was cancelled that day.

The royal palace told AFP it would give details later Tuesday for the visit.

Felipe and Letizia are returning to keep their promise and console survivors in Chiva where the floods ripped away lives and homes, said Vicente Garrido, professor of constitutional law at the University of Valencia.

Residents will be more welcoming on this occasion because "minds are calmer" despite "the enormous pain", and royal visits are "an honour" for any town, he told AFP.

- Monarchy 'strengthened' -

Whereas Sanchez and the Valencia region's leader Carlos Mazon left early last time, the mud-spattered royal couple braved the popular anger to speak with victims.

That gesture was "viewed very positively by everyone" and will afford them "a reception befitting who they are" this week, said Garrido.

Their willingness to travel and risk personal harm earlier this month "strengthens the image" of the monarchy, Garrido said.

Popular ire has instead targeted elected politicians, particularly Mazon because the regions manage the response to natural disasters in Spain's decentralised state.

Local authorities in many cases warned residents of the impending catastrophe too late and stricken towns depended on volunteers for essential supplies for days in the absence of the state.

The conservative Mazon admitted "mistakes" and apologised in the regional parliament on Friday but refused to resign and vowed to lead Valencia's gigantic reconstruction effort.

Sanchez is due to appear in parliament this month to explain the left-wing central government's handling of the floods.