Authorities in Fiji are warning people to prepare for the possibility of widespread destruction, with more than 600,000 people forecast to be in the path of Cyclone Yasa.
The cyclone on Wednesday was upgraded to a category five, the highest possible, with winds at its centre gusting as high as 315km/h.
It is still intensifying, forecasters said, and by the time it reached Fiji's main islands late on Thursday or early on Friday, it would likely be much stronger.
Its projected path would take it right over the two main islands, Viti Levu and Vanua Levu, and disaster authorities were planning for as many as 600,000 people - 66 percent of the population - to be affected.
"Infrastructure could easily wiped out by this magnitude," said Stephen Meke, a lead forecaster at the Fiji Meteorological Service.
Meke said the cyclone's strength was comparable to Cyclone Winston, which killed 44 people and flattened entire villages when it struck the country's north in 2016.
Evacuation centres have already been opened across the country and the government on Wednesday put the military on standby to help.
At a news conference, the director of the National Disaster Management Office, Vasiti Soko, urged people to consider leaving their homes now, particularly those in flimsy houses in crowded informal settlements.
"We can see the cyclone track and we can see the eye and the area that is of concern," she said. "It's the whole of Fiji. Please take heed of warnings."
"If you know that your house cannot withstand any strong winds, let alone a cat 5 cyclone which is on the way, please take yourself and your children to an evacuation centre," she said. "We are pleading that you move before it gets dark."
Schools had been ordered closed, with all senior exams cancelled. Ferry services across the country have been suspended, and public transport in Suva was being pared back. Fiji Airways cancelled most of its flights for the coming days, with the airline evacuating some of its planes to Australia on Wednesday.
Soko urged people to use the narrowing window of time to secure their homes, remove any debris, stock up on supplies or evacuate.
"Please, please tie down your homes, stock up on dry food, stock up on fresh water and ensure the safety of your children," she said.
The cyclone has inched slowly towards Fiji for much of this week, held in place by a high pressure system in the Tasman Sea that allowed it to strengthen in the warm waters. Having completed a loop, it was now inching towards Viti and Vanua Levu at about 15km/h.
Already, there are reports of flooding in several areas. In the western islands of Rotuma, strong winds were already picking up on Wednesday.
Itumata chief Gagaj Manav said it would be a tough few days ahead.
"We were warned two days ago and no one is taking this lightly," he said. "School is cancelled and people had put up shutters and secured their homes."
Yasa is not the first storm to hit Fiji this year. A category five cyclone, Harold, struck the sparsely populated southern islands in April, causing millions of dollars worth of damage.
Cyclone Winston in 2016 caused an estimated US$1.4 billion worth of damage. A cyclone of a similar magnitude striking this year would be particularly devastating.
The coronavirus pandemic and the near complete loss of tourism revenue has crippled the economy by more than 20 percent, severely reducing government revenue and seeing poverty rates skyrocket.
Finance minister Aiyaz Sayed-Khaiyum said the arrival of a category five cyclone was a "worst case scenario." However, he said there was money on hand for an immediate response, and the government was already in talks with development partners.
"Let's pray and hope it changes track, but we are prepared for it," he told reporters in Suva.