Sydney is being smashed by the worst November storm, forcing the cancellation of more than 130 flights and causing chaos for commuters as roads are flooded and train services are cancelled.

This morning, a motorist tragically died on the treacherous roads and two police officers were seriously injured when a tree fell on their car. There have been several other injuries and almost 50 car crashes on roads awash with water.

The city received almost two months of rainfall since 5.30am as a 'supercell' thunderstorm made its way along the east coast.

On the other hand, Transport bosses have urged Sydneysiders to "leave work early" to avoid what is set to be a horror commute home following the largest November storm for more than three decades.

Emergency services have labelled the conditions some of the 'worst' they have ever seen in Sydney.