Damaging heavy swells with sea flooding of low lying areas is also forecast.
Cyclone Winston has already caused damage in parts of Tonga, where it passed the Vava'u today.
Vava'u resident Mark Belvedere, owner of the Eueiki Treasure Island Eco Resort, told the Herald tonight they were facing a big clean-up over the weekend, after the cyclone took a handful of their bungalows.
"We had a little fale at the bottom of the dock that was flown away and a couple of bungalows have gone. Trees are down and there are a lot of coconuts on the ground - there's a tremendous lot to clean up.''
Mr Belvedere said in the town area, powerlines had gone down and buildings badly damaged.
Despite that, he said, they were feeling lucky.
"It feels like we've made it. We've got some damage, but it's a beautiful area here and the downs come with the ups."
So far, there is no sign Winston will head towards New Zealand. Forecasters here say a high ridge over the country over the next few days will bring fairly settled and fine conditions this weekend and through to next week.