Train travel on the Central Coast and Newcastle line will be reduced until further notice due to flooding at Cockle Creek, Transport for NSW said.
Limited buses will replace trains between Cardiff and Wyong.
"A reduced train frequency and changed timetable is operating between Newcastle Interchange and Cardiff, Morisset and Wyong and between Wyong and Central," a Transport for NSW statement said.
"If you are travelling to Warnervale, Wyee or Morisset, change at Wyong for a shuttle train.
"If you are travelling to stations between Dora Creek, Cardiff and Newcastle Interchange, change at Wyong for buses to complete your journey. "
This situation will be "ongoing until further notice".
"If you are travelling to T1 North Shore Line stations change at Hornsby, not Berowra. Please allow plenty of extra travel time and plan ahead at transportnsw.info."
The latest incident followed a week of disruptions for train travellers, amid the weather chaos.
