The country of around 10 million people had barely recovered from last week's battering by rain and winds that killed five people, injured hundreds and left tens of thousands without power.

This week's Storm Leonardo has left one dead in Portugal and lashed the southern Spanish region of Andalusia, where rescuers were searching for a missing woman and evacuated thousands of people.

Scientists say human-driven climate change is increasing the length, intensity and frequency of extreme weather events such as the floods and heatwaves that have struck both countries in recent years.

Portuguese officials issued their highest flood alert for the Tagus in the central Santarem region on Thursday and evacuated people from homes near the river.

Civil Protection chief Mario Silvestre said it was the worst flood threat along the Tagus in nearly three decades.

Local media quoted far-right presidential candidate Andre Ventura as saying he would ask for Sunday's second-round vote to be pushed back a week due to the emergency, as "a matter of equality among all Portuguese".

Any postponement is decided at the municipal level with the approval of the national electoral commission, and Ventura did not provide further details on his proposal.

He is due to face the Socialist favourite Antonio Jose Seguro, who won the January 18 first round, for the mostly ceremonial position.

Seguro told local media: "It is up to the authorities to hold the election in each municipality... I call on the Portuguese people who are able to vote to do so on Sunday."

- 'Everything is ruined' -

In Alcacer do Sal, south of Lisbon, mayor Clarisse Campos told national news agency Lusa that the municipality of around 10,000 electors had decided to postpone voting day by a week.

"The conditions are not in place. We have several isolated localities, and the town centre is completely flooded," she said.

Firefighters waded through the water and used inflatable boats to rescue trapped residents, AFP journalists saw.

Deolinda Guerra, a 78-year-old pensioner evacuated by the rescuers, said: "My house is full of water, everything is ruined: my washing machine, the fridge, everything."

A man in his 60s died in the southeast on Wednesday after being swept away by the current while attempting to drive across a flooded area.

The IPMA weather agency said last month, marked by a string of storms, was Portugal's second-wettest January this century.

- 'We never imagined this' -

Across the border in Spain, Andalusian emergency services said they had dealt with more than 3,200 incidents linked to the storm since Monday as the rain and wind triggered floods, landslides and building collapses.

Rescuers were searching for a woman swept away by a river in the Sayalonga municipality on Wednesday as she tried to rescue her dog from the current.

Authorities were evacuating around 1,500 people from the mountainous municipality of Grazalema, which on Wednesday soaked in as much rain as Madrid usually receives in a year.

Lara Olivar, a 25-year-old actress, told AFP in the village: "We never imagined that this would happen here," as water seeped into garages and homes.

Schools reopened in most of Andalusia after the lifting of the highest weather alert but remained suspended in the worst-hit areas, with road and rail transport still heavily disrupted.

The region's leader Juanma Moreno told reporters that 15 municipalities had been cut off as more than 80 roads were shut.

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