The Otago Regional Council is keeping an extra close watch on river levels over the next 36 hours.

A significant rainfall has been predicted for coastal catchments including Dunedin from tomorrow morning.

Over 100 millimetres is forecast to fall tomorrow and into Saturday, with rivers expected to rise, and surface flooding in low-lying areas, including South Dunedin.

The ORC says the predicted rainfall is similar to that forecast just before Easter this year, but over a shorter period.