The result was quickly welcomed by European Union chief Ursula von der Leyen and French President Emmanuel Macron.

With more than 99 percent of the ballots counted, Seguro had won 66.8 percent of the vote to Ventura's 33.2 percent. That means the 63-year-old Socialist candidate will, as expected, succeed the conservative Marcelo Rebelo de Sousa as president.

The election campaign had been upended by two weeks of storms and fierce gales that killed at least seven people and caused an estimated four billion euros ($4.7 billion) in damage.

The storm disruption forced around 20 of the worst-hit constituencies to postpone the vote by a week, but it went ahead for nearly all the 11 million eligible voters in Portugal and abroad.

"The winners tonight are the Portuguese people and democracy," the president-elect said, pledging to be a leader for "all Portuguese".

Ventura conceded defeat while noting that his party had achieved the "best result in its history."

"We lead the right in Portugal and we will soon govern this country," he told supporters.

EU chief von der Leyen said Portugal had demonstrated its support for "shared European values" remains "strong".

Macron welcomed the result, saying he hoped to reinforce ties between the two countries.

- Storm-hit campaign -

Far-right Ventura, 43, had criticised the government's response to fierce weather and sought in vain to have the entire election postponed.

Ventura is the first extreme-right candidate to make it through to a run-off vote in Portugal.

Seguro is a veteran political operator and former Socialist party leader, having begun his career in the party's youth wing.

In 2014, he lost an internal power struggle, and was pushed out as secretary general of the party by future prime minister Antonio Costa, who is now president of the European Council.

Despite being out of the public eye for the past decade, he never renounced his belief in a "modern and moderate left".

He began his presidential campaign without the backing of the Socialist Party's leadership, though most of them came around to support him.

He slowly climbed in the polls, with one on Wednesday crediting him with 67 percent of voting intentions in the run-off election -- a figure reflected in Sunday's exit polls.

His camp had nevertheless been concerned that the recent foul weather and complacency among his supporters might hurt them.

Earlier Sunday, casting his vote in Caldas de Rainha, where he lives, Seguro said: "Come and vote. Make the most of this window of good weather."

Ventura campaigned on a promise to break with the parties that have governed Portugal for the past 50 years.

Seguro positioned himself as a unifying candidate and warned of a "nightmare" if his opponent won.

- Far right rising -

Seguro took the most votes in the first round of the election in January, in which 11 candidates stood, with 31.1 percent, ahead of Ventura on 23.5 percent. Since no one won a majority, the top two went through to a second round.

Seguro secured the support of many political figures from the far left, centre and the right.

But Prime Minister Luis Montenegro declined to endorse either candidate in the second round. His minority centre-right government relies on support from either the Socialists or the far right to get legislation through parliament.

Ventura's Chega (Enough) party, created as recently as 2019, became the leading opposition force at the May 2025 general election.

He is seeking to "assert himself as the true leader of the Portuguese right", political science professor Jose Santana Pereira told AFP.

In Portugal, the head of state has the power to dissolve parliament and call early elections but otherwise has a largely symbolic role.

The new president will take office in early March.