Tonga's National Weather Forecasting Centre in Tonga says a tropical cyclone alert is now in force for the country.
It warns that people's supply of crops are likely to be affected by the cyclone, which is expected to affect Tongatapu, Vava'u, Ha'apai and 'Eua groups.
Assistant forecaster Ofa Taumoefolau says gales of up to 160km have hit near the island of Tofua, while 285km winds were recorded near Vava'u on Wednesday morning.
He expects staple crops will be damaged by the severe weather, with flooding to low-level areas.
