The storm made landfall on Mozambique's shore early Friday morning local time.
Meanwhile, at least 115 people were killed in Mozambique, Malawi and South Africa after heavy rains affected 843,000 people across southeast Africa, officials and the United Nations said, prompting calls for emergency aid.
The initial system killed at least 66 people due to flooding in Mozambique, Agence France-Presse reported.
The floods in one of Africa's poorest countries have already destroyed 5,756 homes, affecting 15,467 households and 141,325 people.
In Mozambique, 111 people have been injured, 18 hospitals destroyed, 938 classrooms destroyed and 9 763 students affected.
Winds of 167 km/h have accompanied the tropical storm IDAI.
Paul Herbst of IPSS said: "The teams will be supported by Lenmed Maputo Private Hospital in the country today, thereafter heading north to Beira where the cyclone's epicenter will reach land closer to the weekend".
News24 reported that an additional 45 people had died in Malawi as a result of flooding on Wednesday.
"I have lost everything such that only these clothes I am wearing now are my only possessions, nothing else", Dorica Mateba, 83, told Al Jazeera.
Before the storm formed over the Mozambique Channel this week, it was a disturbance that settled over the region and unleashed torrential rains the flooded much of the two neighboring countries.
Mozambique has cancelled flights to several domestic destinations as a tropical cyclone, potentially the strongest to hit the country in almost two decades, approached threatening to bring chaos to southern Africa.
Cyclone Idai is expected to produce winds of up too 200-kilometres an hour.
"Substantial devastation with massive flooding both from river and sea is expected" when Idai makes landfall, South African charity Gift of the Givers said, indicating it was ready to deploy 70 rescue staff, along with 4x4 vehicles, boats, and jetskis to help with rescue efforts.