Tropical Cyclone Winston has changed course and is bringing stormy weather to Tonga.

The Tonga Meteorological Service said strong wind, heavy rain, rough seas, and flash flood warnings remained in force for Tongatapu, 'Eua, Ha'apai, Niuafo'ou, Niuatoputapu and Vava'u.

The cyclone was estimated to have an average wind speed of 120kmh at its centre, with gusts up to 170kmh.

GREG JUST The stormy conditions brought down powerlines in Vava'u.

It has already caused power outages, minor damage and flooding in low-lying areas.

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There were no reports of injuries or casualties, according to Radio New Zealand.

Supplied Power was put out in many parts of Tonga owing to damage caused by Cyclone Winston.

Greg Just, based in Vava'u, said there had been "massive damage to power and phone lines" and "huge tree and crop damage".

Over the last few days the cyclone weakened to a tropical storm, however on February 16 it regained hurricane-force and threatened Tonga and American Samoa.

MetService said the cyclone was category 2.

GREG JUST Damage to a military base in Vava'u.

Over the next 24 hours the cyclone is expected to remain category 2, moving northeast. After that, it's expected to track west towards Fiji.

Kiwis planning travel to the Pacific are advised to keep up to date with the latest forecasts and any severe weather warnings.

In January, a state of emergency was declared in Tonga as Tropical Cyclone Ula passed close by bringing strong winds, heavy rain, and damaging swells.

Are you in Tonga? Email us at newstips@stuff.co.nz.