Tropical Storm Rumbia brought a drenching and strong winds to the march, now an annual outpouring of discontent directed at both China's communist government and the semi-autonomous territory's local leadership.
The parade route from the city's Victoria Park to the skyscrapers of the Central district was a sea of umbrellas as well as banners -- bearing slogans that ranged from "Democracy now" to "Down with the Chinese Communist Party".
Early today, China's national anthem blared as the national and Hong Kong flags were raised outside the harbourside Convention Centre to mark the city's transfer from British to Chinese rule in 1997.
A small but rowdy protest took place near the ceremony with demonstrators burning a photograph of Hong Kong leader Leung Chun-ying, who critics say is guilty of kowtowing to Beijing.
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On the march, one man carried a turtle made out of balloons to represent Leung, who stands accused of retreating inside his shell whenever trouble strikes. Protesters sang "Do You Hear the People Sing?" -- the rabble-rousing anthem from the musical and film "Les Miserables".
The procession came after a survey published by the Hong Kong University found that only 33 per cent of Hong Kongers took pride in being a Chinese national, the lowest level since 1998.
Leung was appointed by a pro-Beijing committee last July, promising to improve governance and uphold the rule of law in the territory of seven million people.
He is charged with overseeing the transition to universal suffrage to appoint the city's chief executive, which was promised by 2017, though critics say little or no progress has been made.
Yeung Yuk, a 28-year-old social worker who was among those marching, said: "People don't want 'elections with Chinese characteristics'. The government should start consultations now so Hong Kong can have genuine democracy."
Leung also promised to address people's grievances, which include a widening income gap fuelled by an influx of mainland Chinese wealth.