Mozambique is braced for another cyclone following the devastation of Cyclone Idai last month, which killed hundreds of people and left thousands homeless.
Cyclone Kenneth is also predicted to hit Tanzania, bringing winds of up to 200km/h (124 mph) and torrential rain.
Authorities in Tanzania have advised people in southern coastal regions to move to safer ground.
Residents have been told to expect damage to their houses and farms.
Cyclone Idai made landfall near the Mozambican port city of Beira on 14 March, packing winds of up to 177 km/h and bringing torrential rain which caused extensive flooding.
More than 700 people were killed in Mozambique, Malawi and Zimbabwe and at least three million were left in need of humanitarian assistance.
Tanzania's Lindi, Mtwara and Ruvuma regions have been listed as the most prone to the weather, which is predicted to hit the country on Thursday.
Authorities have urged people who live in mud houses to seek shelter where they would be safe.
The storm is forecast to also affect Mozambique's northern Cabo Delgado province.
Red Cross and Red Crescent volunteers have been put on alert in Tanzania and Mozambique. And the organisation has alerted communities in northern Mozambique most likely to suffer from flooding and landslides.
Authorities in the island nation of Comoros have closed airports for at least 24 hours as a precautionary measure against the cyclone expected there on Wednesday, reports privately-owned Comores Infos news website.
Schools have also been closed, it adds.
Cyclone Kenneth could be the strongest cyclone ever recorded to make landfall in this region, BBC Weather reports.