There is concern a tropical low brewing off northern Australia may reach cyclone intensity west of Darwin on Boxing Day.
Forecasters said a monsoon was likely to strengthen across the northern Top End during Saturday as a tropical low deepens near the Tiwi Islands.
The trough was expected to be near the Australian coastline during Saturday, then move inland.
There were concerns the low would strengthen as it moved south and would reach tropical cyclone intensity west of Darwin on Sunday.
The system had already brought widespread rain, including a downpour of more than 70mm at Point Stuart in just 30 minutes.
A tropical cyclone advice warning was current for the system, with heavy falls to continue leading to flash flooding during Saturday across northern Arnhem.
Damaging winds with gusts of up to 100 km/h with monsoonal squalls were expected to develop about the coast from Saturday evening.
These conditions could persist, or even increase, during Sunday.
A flood watch was also current for parts of the Top End.
Locations that could be affected include Maningrida, Milingimbi, Ramingining, Galiwinku, Warruwi and Gunbalanya.
Northern Territory Emergency Service advised people to secure loose outside objects and seek shelter when conditions deteriorate.
Residents have been urged to create their own sandbags if there was flooding and to stay away from flooded drains, rivers, streams and waterways.
