The director of Tonga's met service, Ofa Faanunu, says Cyclone Wilma is now heading towards the main island of Tongatapu.
The category 3 storm passed to the eastern side of Vava'u before directly hitting the Haapai islands group this morning where it caused damage..
Ofa Faanunu says the cyclone also looks to brush Eua.
"So we are already been affected right now as we speak and we expected to pick up by this afternoon and we'll see what happens by tonight. And the people have been informed. The diaster management committee has been activated and I think the residents of Tongatapu and Eua should be ready."
Ofa Faanunu says when the cyclone departs Tonga, it is expected to head towards Fiji's south eastern Lau islands.
The New Zealand foreign minister, Murray McCully, was to travel to Tonga but the trip has been put off.
Mr McCully's office says his flight was cancelled because of the strenghthening cyclone.
He was scheduled to meet the country's new ministers but the visit will be rescheduled.
Emergency teams are out clearing and assessing the damage from Cyclone Wilma in American Samoa despite ongoing bad weather.
The eye of the cyclone passed over Tutuila yesterday and caused damage to power lines and telecommunication outages, minor landslides and damage to homes and roofs.
Most businesses and all schools as well as Pago Pago International Airport remain closed with all flights cancelled.
Our correspondent in American Samoa, Fili Sagapolutele, says northern villages and businesses on the island are reportedly the worst affected by the cyclone.
Reports have been coming in of several damage to homes, especially the roof being torn off, there's a lot of debris on the road, [and] fallen trees. And the government and officials are working to clear a lot of it. But it's not helping because of a new system that headed into the territory as of this morning and that's causing a lot more rain and also high winds and that's another concern.
Fili Sagapolutele says there was only one weather related injury reported, but no deaths.