Police say they are still trying to find a man they believe abandoned his car in floodwaters near Byron Bay in northern New South Wales last month.

The car, which belonged to 29-year-old Charl Viviers, was found abandoned on a flooded road at Repentance Creek on January 31.

It was found unlocked and the interior was wet, and police think it was abandoned after the motor stalled in floodwaters.

Police say they have concerns for his health as he needs regular medication.

Mr Viviers is described as having a slim build and dark hair with a beard.