Intense Tropical Cyclone Idai was one of the worst tropical cyclones on record to affect Africa and the Southern Hemisphere. The long-lived storm caused catastrophic damage, and a humanitarian crisis in Mozambique, Zimbabwe, and Malawi, leaving more than 1,500 people dead and many more missing. Idai is the deadliest tropical cyclone recorded in the South-West Indian Ocean basin. In the Southern Hemisphere, which includes the Australian, South Pacific, and South Atlantic basins, Idai ranks as the second-deadliest tropical cyclone on record. The only system with a higher death toll is the 1973 Flores cyclone that killed 1,650 off the coast of Indonesia.

A tropical cyclone is a rapidly rotating storm system with a low-pressure center, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Depending on its location and strength, a tropical cyclone is called a hurricane, typhoon, tropical storm, cyclonic storm, tropical depression, or simply cyclone. A hurricane is a strong tropical cyclone that occurs in the Atlantic Ocean or northeastern Pacific Ocean, and a typhoon occurs in the northwestern Pacific Ocean. In the Indian Ocean and South Pacific, comparable storms are referred to as "tropical cyclones". In modern times, on average around 80 to 90 named tropical cyclones form each year around the world, over half of which develop hurricane-force winds of 65 kn or more. Tropical cyclones carry heat away from the tropics and transport it towards temperate latitudes. This plays an important role in regulating global climate. Tropical cyclones can be very harmful for people.