Updated March 04, 2017 18:43:06

Photo: A tropical low off the Northern Territory coast is expected to become a cyclone. (Bureau of Meteorology )

A tropical cyclone warning has been issued for Darwin and surrounding coastal and island communities, including the Tiwi and Croker islands.

Darwin and the north-west coast of the Territory have been on cyclone watch throughout Saturday.

But the Bureau of Meteorology have upgraded the warning due to the intensity of the tropical low weather system approaching the coast.

The low is expected to pass over the Tiwi Islands tonight and potentially turn into a Tropical Cyclone on Sunday.

Earlier, regional director of BOM NT, Todd Smith, said he was expecting heavy rain to pick up from Sunday morning in Darwin, or possibly overnight on Saturday.

"People need to be careful if they're in coastal areas," he said.

Mr Smith said the Twi Islands had already begun to experience wet conditions.

"The very heavy rain is going to continue for at least the next 24 hours and probably for the Tiwis begin to ease as they head into Monday," he said.

"But certainly the next 24 hours is the time for people to take care."

Mr Smith also warned that as well as heavy rain and gale winds, the weather system may result in higher tides than usual on the Tiwi Islands.

A tracking map released by the bureau forecasts the storm will become a category two system after it passes Darwin and is offshore from the Daly River mouth.

Photo: The tropical low is expected to develop into a cyclone on Sunday. (Supplied: Bureau of Meteorology)

The likelihood of the tropical low becoming a tropical cyclone has now been put at high for both Sunday and Monday, meaning a greater than 50 per cent chance.

If the low develops into a cyclone the storm will be known as Tropical Cyclone Blanche.

Topics: cyclone, weather, darwin-0800, nt

First posted March 04, 2017 13:07:01