More than 600,000 people in Mozambique could be affected by Cyclone Freddy, which is expected to make landfall in the coastal provinces this week, the authorities say.
The areas considered most at risk are the Zambezi valley, central regions and the southern Inhambane province.
At least 100,000 people will require state assistance should the cyclone hit at full strength, according to Agostinho Vilanculos, who heads the water resources department.
At a National Centre for Emergency Operations meeting, he described the tropical storm as an intense weather system with wind gusts of between 280km (174 miles) and 290km per hour.
In the coastal city of Beira, residents have been fortifying their homes with sandbags and placing metal sheets on windows as well as pruning trees in backyards.
They have also been stocking on food and water along with supplies of candles and lanterns.