The Yallourn open cut mine in Gippsland has been affected by heavy rain.
Last year the Yallourn mine was flooded when the Morwell River diversion failed, releasing water into the open cut mine.
The collapse resulted in massive repair works, which still have not been finished.
After nearly a week of heavy rain there is water in the mine again.
One coal conveyor has been flooded and will be out of action for about three weeks.
Mine operator Energy Australia says coal is being transported to the power station by another conveyor and no generating units have been affected.
It says there has been no damage to the repair works but construction has stopped until the weather eases.
It says the mine will be vulnerable to flooding until the repair work is finished.
© ABC 2013
15:51 EDT Forecasts still suggest Christmas Day in Australia will be typically hot, humid and thundery in the north, windy in the south, wet in the southeast and dry and warm on the west coast.