At its peak, ex-tropical Cyclone Trevor was as powerful as 1974's devastating Cyclone Tracy, with wind gusts of up to 250 kilometres per hour.

Key points: Cyclone Trevor reached an intensity similar to Cyclone Tracy before downgrading to a tropical low inland

Cyclone Trevor reached an intensity similar to Cyclone Tracy before downgrading to a tropical low inland Heavy rain with falls up to 100 to 200mm are possible within an area around 200km either side of the system

Heavy rain with falls up to 100 to 200mm are possible within an area around 200km either side of the system Groote Eylandt has been surveyed and has not sustained any damage, so residents will be returning on Sunday by plane

The storm crossed the Top End coast late on Saturday morning as a category four, downgrading to a tropical low early on Sunday morning, after tracking to the south-west and moving inland through the Carpentaria district.

On Sunday morning, the storm was to the north-east of Tennant Creek.

There have been no known deaths, major injuries, or major damage to infrastructure, said Chief Minister Michael Gunner on Sunday.

Ex-Tropical Cyclone Trevor has been downgraded to a tropical low. ( Supplied: BOM )

"The winds around the system itself do have the potential to be damaging still; we do have a severe weather warning out and that's for damaging winds and also locally destructive winds around the system," Bureau of Meteorology duty forecaster Nicholas Loveday said.

"The locally damaging winds are most likely to occur, if they do, in thunderstorms which are feeding into that tropical low during today and tomorrow."

Heavy rain with falls of 100 to 200 millimetres is possible within an area around 200 kilometres either side of the tropical low.

"We estimate the winds around the eye peaked at 175kph mean winds, and those winds were gusting to 250kph," he said.

"To put that into context, that's roughly the same intensity Cyclone Tracy had around its eye.

"It was very lucky that it made landfall to the east of Borroloola and Port McArthur, so it did spare those towns from experiencing the worst.

"It is pretty scary, and that helped explain why the evacuations occurred: even if the strongest winds didn't occur at those towns itself, it's just such a huge risk that it makes sense to keep those people safe."

Cylone Tracy's official death toll is 71, but theories have abounded for decades that the real number was much higher.

Ex-Tropical Cyclone Trevor is now a tropical low in the central Top End. ( Supplied: RAMMB )

Large, 'well organised' storm

Mr Loveday said the weakening of the category four storm was fairly standard.

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"It did make its way a fair way inland and that's because it was such a large system and it was very well organised and well stacked," he said.

"The other thing which helped was the topography around that area is fairly flat, so there was less friction to slow the system down, so it did make its way a fair way inland."

There was significant rainfall across the Northern Territory overnight, with 114mm recorded at McArthur River mine, although Mr Loveday noted the BOM only has a limited number of observation points in that region.

"As Trevor moved further south it did help increase the weather around Darwin, it helped induce a nice moist onshore maritime flow, and that really boosted up the rainfall totals around the coastal areas around the Top End," he said.

"So Charles Point came in with 148mm, which is pretty significant."

On Sunday, Trevor is expected to track south through the Barkly district, likely remaining to the east of Tennant Creek, bringing heavy rainfall and damaging winds with it as it moves.

Tennant Creek Civic Hall will be open to provide emergency shelter for community members who do not have adequate shelter or have concerns regarding their current housing arrangements in the case of the predicted severe weather.

At this stage, community members have not been issued a directive to seek shelter.

People sift through donations for clean clothes at the evacuation shelter in Darwin. ( ABC News: Shani Wellington )

'You cannot simply pray and hope'

The Chief Minister paid tribute to emergency services, police, Defence and government workers for their role in keeping people safe.

"You cannot simply pray and hope for these things, a lot of work has to happen, an incredible professional effort was put in place," Mr Gunner said.

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"You think about how many pieces were moving on that map, and the timeframe in which police and others had to operate, the evacuation that was done, an incredible number of people over a short span of time … where the miracle was required was for those people who did not cooperate with police.

"If you followed instructions, as we've now seen, you were safe, and that's all we could ever ask for from our hardworking people here, to make sure we did everything we could to keep Territorians safe.

"We can build new houses, we can put in new roads, we can put power lines back; your lives are precious.

"There was an incredible amount of work done so that we could stand here and say 'no known major injuries' and that's always what you want to be able to do."

Mr Gunner said the cost of the operation was not yet known.

"The priority at the moment is to get those government services back up, get schools back open, get people home — a return to normalcy," he said.

"We know that we can recover."

Northern Territory Chief Minister Michael Gunner (L) speaks to people flown from Borroloola to Darwin during Cyclone Trevor. ( ABC News: Shahni Wellington )

Focus on restoring power, water, telecommunications

SecureNT Regional Controller Commander Travis Wurst said despite the fact that some areas were no longer feeling the effects of Trevor, "it doesn't mean all communities have been given the all clear".

Around 2,100 evacuees registered with the NT Government at shelters in Katherine, Tennant Creek, Darwin and Nhulunbuy, and many others who self-evacuated were not included in that figure.

A 130-bed shelter at the Tennant Creek High School housed those from remote outstations.

McArthur River mine workers are bunkering down as the cyclone passes to its east. ( ABC News: Kristy O'Brien )

Six emergency services teams are flying over the area to inspect the damage, and will check on the six people that remained in the region.

At McArthur River mine, about 100 kilometres from the coast and to the west of the cyclone forecast track, a bunker housed more than 60 people.

Groote Eylandt has been surveyed and has not sustained any damage, and 100 residents have already flown home.

"These residents will be eligible for relief payments from their community after arrival. Bickerton Island residents are not yet cleared for return, this will be assessed tomorrow," Commander Wurst said.

Cyclone Trevor makes landfall near the NT-Queensland border. ( Supplied: Google Earth )

The Roper Highway has reopened and residents are allowed to return to Ngukurr tonight, but not Numbulwar; those residents in Katherine will begin bussing home from Monday, and would be able to access relief payments once they get home.

Payments to registered evacuees will be $503 per adult, $20 per child, with a maximum of $1,066 per family on a debit card system.

Borroloola and Robinson River areas will be inspected by safety teams from this morning, with Borroloola the priority, Mr Wurst said.

"We have people surveying those communities and the connecting roads that were affected by Severe Tropical Cyclone Trevor," he said.

"One of the things that we're concerned about is preserving vital infrastructure for these remote areas and restoring telecommunications, power and water to communities that have had their supplies affected."

Heavy rain is likely to cause significant stream rises and localised flooding in the eastern Carpentaria and northern Barkly districts tomorrow. A flood watch has been issued for Carpentaria Coastal Rivers, Georgina River and the Barkly in the Northern Territory.

Alice Springs and the Todd River catchment area should not be significantly impacted.

'Like a small tornado'

Several tents at the Katherine evacuation centre were blown over in a serious lightning storm last night, forcing many Cyclone Trevor evacuees to shelter elsewhere.

The storm left behind a huge mess for emergency services, who found upended tents, tents in trees, tent poles stuck in a building roof, bent road signs and other debris across the showgrounds site.

Tents were blown onto a house roof in Katherine. ( Supplied )

Urupanga resident Richard Collins said the storm terrified his children and the tents should have been better secured.

"You've got to peg them down — if you want to use a tent you've got to do it properly," he said.

"It was scary there today, very scary … It was like a small tornado."

Katherine's Emergency Controller, Superintendent Daniel Shean, said he was not aware of any serious injuries to evacuees.

"There are tents that were upturned, there is damage to some of the buildings as a result of that storm," he said.

"We've taken control of that site so that we can regroup and make sure that people are safe."

Richard Collins (second from right) said his children were frightened by the storm. ( ABC News: Felicity James )

Superintendent Shean said they would find alternative places for people to sleep at the showgrounds site because that is where the meals and other services are based.

The tents had been set up with help from the nearby Tindal RAAF base to sleep about 600 evacuees from remote coastal communities including Ngukurr, Urupanga, Numbulwar, and Borroloola.

The Defence Force was called back in to assist with re-erecting the tents.

Some evacuees left the evacuation centre overnight because of the damage, either temporarily or to stay elsewhere.

Just an hour before the storm took residents and evacuation centre managers by surprise, Superintendent Shean gave all residents an update about damage to their communities.

"It looks like Numbulwar is good with no damage," he said, which was met with loud cheers and clapping.

Vets from the Roper Gulf Regional Council then told the gathering they would attend all evacuated communities to check on dogs and other pets left behind.