By Joseph Winter
BBC News, Pretoria
Zuma supporters were determined to have a good time - whatever the weather
Thousands of people went to the Union Buildings in South Africa's capital, Pretoria, to see their new president - and also to enjoy a free, open-air concert.
Nobuhle Sithole travelled for nine hours overnight from Durban and arrived at 0530, while it was still dark.
She was still dancing in the afternoon - and right onto the evening.
Mr Zuma went out of his way to praise his predecessor, Thabo Mbeki
"I still have energy to dance because I am so happy," she said.
But the exertions had proved too much for some of her friends, who were curled up under blankets on the grass in front of her.
Jacob Zuma normally enjoys partying as much as anyone, but on his first day as president he was relatively restrained.
When he came down from the official ceremony to greet his supporters, the crowd started singing his trademark Umshini Wami (Bring Me My Machine Gun) hoping he would join in as usual.
But he declined and by his high crowd-wowing standards was relatively subdued and statesmanlike.
"He showed he is now a president," said Seipati Kau, as she dried off in the sun following an early morning downpour.
While some were disappointed, Ms Kau fully approved of Mr Zuma's new presidential demeanour.
"That was a song for the struggle, not for now," she said.
But the party continued even without the president.
'I was there'
Some of South Africa's best known entertainers, including Loyiso Bala, DJ Oskido and PJ Powers kept everybody grooving away.
The music represented South Africa's rich cultural diversity - rock 'n' roll to traditional Zulu singers to house and kwaito - the music of young, urban people.
South Africans of all ages joined the party
Many of those who attended were political activists wearing the yellow, green and black of the ruling African National Congress.
But there were also families enjoying the music while having picnics on the grass and fathers carrying their children on their shoulders - too young to appreciate the significance of the occasion but who will still be able to say: "I was there."
And long after Mr Zuma had left to join the banquet for the heads of state and other dignitaries, crowds of people were still streaming towards the Union Buildings - those for whom a free concert was more of an attraction than a presidential inauguration.
"We watched the speech on television and then came along for the show," said one young man hurrying along with his girlfriend.
Just after Mr Zuma had arrived in the morning, a crack of thunder boomed out from the heavens.
But the torrential downpour which followed failed to dampen the enthusiasm of the crowds.
"When it rains before a big event, there is a Zulu saying: 'Ilamagu Livumile', which means: 'The ancestors have given their blessing'," Nankhithe Mapheele said as she watched the festivities, sheltering under an umbrella.
As the skies opened, some sought shelter under the trees in the lawns of the Union Buildings.
But others continued to sing and dance in the rain.
One young man even managed to continue dancing, while holding a fold-up director's chair over his head to protect himself from the deluge.
On the massive specially erected open-air stage, the cultural dancers also continued to perform.
But by the time Mr Zuma took the oath of office, the sun was shining brightly.
Even a slightly restrained Mr Zuma still has the popular touch.
"We are rejoicing. He's the people's leader," said Nkompela Xolile.
"He knows the poor of this country, those who live in rural areas. And he will help them."
Rain before a big event is a good sign in Zulu tradition
"I didn't sleep last night, I was so excited," said Sophie Zigalala, while her young daughter danced on the grass.
"If he is president, people will find a job. The people are suffering."
One of the many songs praising South Africa's new leader runs: My mother was a kitchen girl / My father was a garden boy / That's why I'm president.
People hope that his humble origins mean he will do more than the last elected leader, Thabo Mbeki, for the millions of South Africans living in poverty.
Indeed, the crowd booed every mention of the name of Mr Mbeki, who lost a bitter power struggle with Mr Zuma for the leadership of the ANC and then the country.
But again, Mr Zuma showed his statesmanlike side - going out of his way to praise Mr Mbeki's vision and leadership during his time in office.
Mr Zuma's supporters fervently believe that allies of Mr Mbeki invented spurious charges of corruption and rape to block his rise to the presidency.
Mr Zuma was acquitted of rape after a trial in 2006, and corruption charges against him were dropped earlier this year.
The celebrations were colourful
"After all the things people have done to him, he will prove people wrong," said Ms Kau.
The first word most people mention when asked what they want from their new leader is "jobs".
But with the economy entering its first recession since the end of apartheid in 1994, it will not be easy to meet the huge expectations people have of their new leader.
Mr Zuma acknowledged this.
"There is a lot to be done," he said, before saying the government would not rest until the key problems of Aids, poverty, lack of essential services, poor education and unemployment had been tackled.
He promised to work hard and "shun laziness and incompetence" to meet these challenges and to take action against any member of the government not pulling their weight.
But in the short term, festivities continued with an official cultural evening in the Monte Casino in Johannesburg, as radio stations advertised the "inauguration after-party" for those who still had any energy left to dance.