Cyclone Trevor has struck the Northern Territory as a category four system, hammering remote communities with destructive 250 km/h winds and torrential rain.

It was one of two monster storm fronts bearing down on northern Australia this weekend – cyclone Veronica was hurtling towards the Pilbara region in Western Australia.

The NT chief minister, Michael Gunner, visited an evacuation centre in Darwin on Saturday morning and said the people were calm. He had declared a state of emergency earlier this week.

“We are expecting a large recovery effort,” Gunner told reporters.

“There are lot of volunteers and emergency services workers busting their guts to ensure everybody is being looked after.”

Trevor was bringing “very destructive” winds at Centre Island, off the coast of Borroloola, the Bureau of Meteorology said.

The storm core was just south of the Pellew Islands, and the system stretched to Mornington Island in Queensland.

“It looks like the centre of Cyclone Trevor is going to be passing fairly close to Borroloola,” the Bureau of Meteorology forecaster Shane Kennedy said.

The Northern Territory incident controller Brendan Muldoon told ABC Darwin radio on Saturday morning Trevor was hitting between NT’s Port McArthur and the Queensland border.

Muldoon said it would hit McArthur River Mine as a category two or three system about 7pm (local time) on Saturday night.

Between 100 to 200 millimetres of rain a day was expected along with isolated falls of up 350mm.

The Carpentaria highway, Roper highway, Barkley stock route and the Tablelands highway had been closed, and some reports said this was frustrating some pastoralists trying to move their cattle to safer ground.

William McMillan decided not to evacuate from Calvert Hills cattle station near the Queensland border, because he was worried about poor access getting back.

He was about 80km south of the eye of the storm.

“It’s getting a little bit hectic,” he told ABC radio. “Only had 20mm of rain so far but it’s on its way.”

His wife and children had gone to Conclurry, Queensland.

“I’ve put all the kids toys under cover ... (you don’t want) a trampoline flying through a window,” he said, adding that the cattle were in good physical condition.

Muldoon said four people on Vanderlin Island had refused to leave and six had opted to stay behind at Borroloola, against advice.

The regional controller Travis Wurst urged people to stay inside even after the storm front had passed.

“Even though the cyclone may have left the area where you are, we’d urge you not to go outside to explore the damage. There may be downed power lines or other hazards. We don’t want to see anyone putting themselves in danger,” he said.

Muldoon said survey teams were on standby at strategic locations to assess the damage and restore critical infrastructure such as power and water when safe.

They would also be ensuring that airfields were clear for planes to land to bring in supplies.

He urged people in the path of the storm to heed the advice of emergency services.

“Bunker down, this is going to be a very significant system, we’re looking at a cyclone reaching 300 to 400 kilometres from the eye of the storm on both sides,” he said.

Those still on cattle stations were likely to be cut off by flooding, Muldoon warned, and would need to have enough food and water supplies.

“I would, if you’re able to leave, be leaving those areas,” he said.

By Sunday afternoon, forecasters believe Trevor would have weakened below cyclone strength, reaching Tennant Creek, 1000km south of Darwin, as a tropical low in the evening.

An evacuation centre was being set up in Tennant Creek for those from 14 nearby outstations.

Muldoon urged people at Darwin evacuation centres to sit tight. Information would be released on Saturday about when they could head back to their homes.

“We don’t want planes leaving Darwin half full,” he said.

He indicated that Groote Eylandt residents might be able to head home as early as Sunday.

In Western Australia, people in Port Hedland and Karratha were bunkering down for Cyclone Veronica, which was also expected to be a category four system and was due to hit the Pilbara region about 8am AWST on Sunday.

“Mixture of nerves and anticipation It’s definitely calm before the storm at the moment,” Lucy Guy told the Guardian.

She was waiting out the storm at South Hedland with her fiance.

“Our power is underground so hopefully we can keep watching Netflix,” she said.

“Roads are starting to flood from rainfall already and it’s still around 20 hours until the real fun starts.”