An early thunderstorm and late scattered showers threatened to mute festivities but hundreds of thousands of buoyant revellers kept spirits high for the record-breaking midnight show.

Under the banner of "the pulse of Sydney", the Harbour Bridge again played centrepiece as 6000 fireworks and other features were fired from it during the 12-minute program.

More than 8.5 tonnes of fireworks were set off over the harbour, including 35,000 shooting comets and new designs that allowed gold palms to change colour mid-explosion.

Lime and peach were two unusual colours used while silver won out over gold for the famed waterfall effect off the bridge floor.

An estimated one million people watched from city streets, bars, backyards and crammed harbour vantage points, including at the Sydney Opera House and Kirribilli, for a glimpse of the pyrotechnics.

Alexandria woman Sadhbh Warren, who managed to squeeze into Barangaroo after 9pm despite train delays, said the spotty rain didn't affect revellers too much.

"The crowd are just popping on their glowsticks over their ponchos and ignoring it; lots of people dancing and kids up way past their bedtime," she told AAP.

German traveller Anja Ebert arrived early to Mrs Macquaries Chair to fulfil "a huge dream" to see the Sydney NYE fireworks display, while IT programmer Amit Phaltankar bunkered down at Blues Point Reserve from 4pm for his first NYE show in Sydney.

"The fireworks were just awesome," Mr Phaltankar told AAP.

Earlier in the night, kids and people with early bedtimes were treated to a sneak peak of the new designs and the Jewel of the Sea firework, based off a drawing by South Australian schoolgirl Dhrithi.

Primary schooler Siena Raynham was wowed by the size of the show while her younger sister Sophie loved the show "because it was very exciting".

The bridge pylons were lit up soon after for a new segment called Calling Country that honoured Australia's indigenous heritage.

Revellers also got an extra light show earlier in the night as thunderstorms lit up the sky and dumped more than 8mm of rain on those who'd settled into early vantage points.

Lightning strikes at Central train station also caused havoc for several lines of the city's rail network.

Some commuters spent close to an hour on stationary trains while many others were delayed as urgent signal repairs went on until 8.30pm.

Sydney's New Year's Eve fireworks show is Australia's largest public event, requires 15 months of planning, 60 kilometres of wiring and cabling, and is watched by an estimated one billion across the globe.

Destination NSW says its research found the event contributes $133 million to the local economy.

Australian Associated Press