A large area across the Top End coastline including numerous communities has been placed on cyclone warning or watch, which means destructive weather is expected in 24 to 48 hours.

A tropical low north of Elcho Island in the Arafura Sea has been moving slowly west and intensifying.

Tropical Cyclone Claudia is expected to form early Thursday and cross the coast as a Category Two system by early Friday, but cyclone movements are notoriously unpredictable.

That will bring damaging waves, dangerous flooding and wind gusts that can cause damage to houses, trees, caravans and crops, and power outages.

Populated areas expected to cop the brunt of the cyclone include remote indigenous coastal communities at Croker Island, Goulburn Island, Maningrida - home to more than 3000 people - and Milingimbi.

Other places at risk are Dundee Beach, Gunbalanya, the Tiwi Islands, Jabiru and Nhulunbuy.

"Darwin will go on to cyclone watch because there's a chance there may be gale force winds impacting the Darwin area from later on Friday," Bureau of Meteorology acting NT manager Jude Scott said.

"From Friday evening into Saturday the weather will deteriorate in the Darwin region, we can expect very heavy rainfall and potentially dangerous squally thunderstorms."

While the cyclone was not expected to form until Thursday, heavy rainfall and localised flooding were expected from Wednesday.

People in remote communities need to be ready now with survival plans and kits, NT Police Assistant Commissioner Michael Hebb said.

Chief Minister Michael Gunner said he could assure the people of Arnhem Land and other affected areas that "everything was being done to ensure the safety of residents and communities".

The Territory Emergency Management Council - including police, emergency services and NT government agencies - has been activated to deal with the cyclone's potential effects including medical help for casualties, he said.

The effects of Cyclone Trevor last year, which fortunately missed populated areas, and the more destructive Marcus that hit Darwin in 2018 were fresh in people's minds and the NT was prepared, Mr Gunner said.

"There are shelters available in these communities, additionally remote housing constructed in recent years can withstand cyclones up to category four," Mr Gunner said.

"Many communities are more resilient and better able to withstand cyclones without the need for evacuation."

Mr Hebb said people should have cyclone kits with food, drink, torches, a radio, first aid and other essentials for families for up to 72 hours in case they become isolated.

He said people should monitor emergency websites such as securent.nt.gov.au and ABC radio, and not cross flooded roads or go out in boats.

Australian Associated Press