Heavy rain, flash flooding and traffic queues have caused havoc on the roads into and around Sydney after the new year's break.
Some of the city's major arterial roads were under water in the mid-afternoon, as 10mm fell in some parts of the city within 10 minutes on Sunday afternoon.
The M1 Pacific Motorway on the Central Coast faced significant delays early in the afternoon after several cars crashed near the Tuggerah interchange.
All northbound lanes were closed for about an hour while the accident was cleared. Although one lane was eventually opened, traffic was queued for about five kilometres several hours later.
The same motorway southbound also faced delays after heavy rain caused cautious motorists to slow down, sometimes to 40km/h in the 100km/h zone.
At 3.50pm, there were significant queues in the state's north, with southbound traffic queued for 13.5 kilometres at Macksville, adding an extra hour and five minutes to journeys, while cars driving north faced a queue of 1.5 kilometres.
At Woodburn, south of Lismore, travellers were queued for five kilometres, adding 45 minutes to their journeys.
Nicquie Sinclair, a spokeswoman for the Transport Management Centre, said the delays were due to the weather and heavy holiday traffic returning to Sydney.
"People are driving slower through the heavy rain," Ms Sinclair said.
"A lot of people are coming down into Sydney because work starts again tomorrow. The traffic is definitely improving now [as the afternoon goes on]."
However, as holiday traffic began to ease in the mid-afternoon, flash flooding set in around the city, affecting roads in a wide circle from Bondi to Northmead.
The flooding was present on Newbridge Road at Moorebank, The Horsley Drive at Fairfield, Marsden Road at Carlingford, Victoria Road westbound at West Ryde, the Cumberland Highway at Northmead; and the Western Distributor at Pyrmont in both directions.
Kim Westcott, a meteorologist for Fairfax Media's Weatherzone, said Bankstown and Sydney Olympic Park had some of the heaviest rainfall.
"Out of all that rain that Sydney Olympic Park got, 10mm fell in 10 minutes at 3pm. That's really heavy," Ms Westcott said.
"And we had 6mm fall in 10 minutes at Bankstown and Horsley Park."
Showers washed out most of the afternoon's cricket during the third Test between Australia and the West Indies.
As the return to work beckons on Monday, commuters have been advised to bring an umbrella.
"We are going to see more rain tomorrow and on Tuesday, easing off into showers on Wednesday and Thursday. We're in for a wet few days."