The heavy rains on Thursday night have cut the South Coast rail line south of Wollongong.
Flooding at Oak Flats and Port Kembla have seen train services suspended between Wollongong and Shellharbour Junction and Wollongong and Port Kembla.
A shuttle train is in operation between Shellharbour Junction and Kiama.
Footage sent to the Mercury from a rail commuter at Dapto showed the extent of the flooding in the area, with water lapping up to the edges of the rail line.
Meanwhile, the Illawarra Highway between Princes Highway and Tongarra Road is closed in both directions and is expected to remain closed for several days.
Macquarie Pass and the Illawarra Highway between Jamberoo Mountain Road and Broughton Avenue is closed in both directions due to flooding.
The pass is expected to remain closed for at least most of Friday.
Detours are in place for light vehicles via Jamberoo Mountain Road and, for heavy vehicles via Picton Road.