Samoa is in recovery mode after Cyclone Gita ravaged the island nation and now the storm system has Tonga in its sights.

The now Category 3 storm brought damaging winds and heavy rain, and forecasters say there's a chance New Zealand could also be in the firing line.

Most of Samoa's capital city, Apia, is now under water. Roads have turned to rivers and residents have been forced to wade through the flood for supplies.

"When we tried to access evacuation centres yesterday we almost couldn't make it through," says Red Cross secretary general Namulauulu Tautala Mauala.

"We had to use our pickup truck."

While many areas are closed off, people still braved the conditions using cars, trucks and even bicycles to get around.

Several buildings have been flattened and authorities say more than 300 people have been evacuated.

"A lot of families have lost their homes and some have evacuated into their extended family's homes," Ms Mauala says.

So far there have been no reports of serious injury or death. Five evacuation centres have been opened to residents and Red Cross workers have been going door to door.

While the worst of the cyclone may have passed, Ms Mauala says there are still concerns for those in the outer islands and low lying areas.

"There's no power and electricity in the whole country except for essential areas, so from the Red Cross we know that there will be a lot of problems for water and sanitation."

Cyclone Gita passed over Samoa as a Category 1 storm system. Since then it's been upgraded to Category 3 and could go higher. Tonga is its next target.

"Without question it's a stronger storm," says NIWA's Chris Brandolino.

"There's a very good chance, if not a likelihood, there'll be more wind damage and with a stronger storm and higher winds there's bigger waves and more chance of coastal inundation."

It's then expected to move south and could turn east during the next week.

NIWA says that means there's a "distinct possibility" it could hit New Zealand, but what form it will take still isn't known.

"Whether it falls apart before it gets close to New Zealand, or whether it remains a somewhat formidable system... Again, if it were to impact New Zealand it would be an ex-tropical cyclone," Mr Brandolino says.

That's exactly what Fehi was when it hit New Zealand a fortnight ago and much of the country is still recovering from that.

Newshub.