Cyclone Jasmine is causing flooding around Tonga's main island of Tongatapu.
It is the second cyclone to affect Tonga in a week.
Jasmine, which had been a category three storm when it passed through Vanuatu waters late last week, is now a category one.
It will approach Tongatapu today with wind gusts of up to 90 kilometres an hour near its centre.
Our correspondent, Mateni Tapueluelu, says flooding is more of a concern than the wind.
"Because Tonga has been hit by flooding over the past two weeks, particularly the low lying areas. In fact on the west part of Nuku'alofa they had to cut new roads [channels] to ensure that the floods just flow away to the sea."
Mateni Tapueluelu says the successive cyclones have also impacted on the breadfruit harvest.