Weather forecasters in the Pacific have upgraded Tropical Cyclone Winston from Category 4 to 5.
It's now heading towards Fiji after causing extensive damage in Tonga, where at least 10 homes have been destroyed and another 200 have been seriously damaged.
The northern islands of Vava'u have been worst hit, with disaster officials fearing crop damage could lead to a food shortage. Even those in the capital are taking precautions.
Taking refuge in their place of worship, Seini Mafi and her family moved out of home and into the church to shelter from the storm.
"It's just more important for us to prepare ourselves earlier," Ms Mafi says. "When it comes, we are here and we are safe with our children and families."
The slow-moving Cyclone Winston has been sweeping across the northern islands of Vava'u.
Disaster officials say 2500 residents there have also moved to evacuation centres.
"About 10 houses were destroyed, and close to 200 houses suffer some damage one way or the other," says emergency management officer director Leveni Aho.
His biggest concern, however, is widespread damage to the agricultural sector.
"It's estimated this morning it affects about 85 percent [of the fruit crops] and the root crops it affects about 60 percent," says Mr Aho.
(The Boatyard: Vava'u / Facebook)
Domestic flights are either cancelled or delayed.
The only one managing to reach the capital today was from Ha'apai, a group of islands hit by a Category 4 storm in 2014.
"Yeah, it's very rough. Lots of wind, lots of rain. I'm surprised that the plane made it," says stranded passenger Malekai Kaufusi.
Tourists spoke of huge swells lashing the coastline.
"The beach is gone. We had so much beach, like 40 to 50 metres. But it's just totally gone," says Andreas Klemmer.
Tonga is also in the grip of a Zika outbreak.
Rubbish clean-ups to contain the spread are continuing, but Winston is only adding to worries.
The fear is that Cyclone Winston could exacerbate the Zika virus threat. Ensuring people have clean water, sanitation and food will be critical in the aftermath of the storm.
As Winston moves away from Tongan waters, forecasters say Fiji could be next in line.