Cyclone Idai, the storm that has killed hundreds of people, submerged homes and battered cities in southeastern Africa, may prove to be one of the worst weather-related disasters ever in the Southern Hemisphere, a United Nations official said on Tuesday.

Officials with global aid groups and in Mozambique, where the storm hit hardest, are only beginning to reckon with its destruction. Potentially 1.7 million people were in the direct path of the cyclone, the United Nations estimated on Tuesday, and rain is forecast to continue in parts of the region for several days.

[Rescue workers struggled as heavy rains swelled rivers and isolated flooded communities.]

Herve Verhoosel, a spokesman for the United Nations World Food Program, said in an interview that the agency’s workers had described seeing “water and water for miles and miles” — flooding so severe it resembled an inland ocean where homes and towns had stood.

The situation remained dire, he said, for potentially hundreds of thousands of people in need of food, clean water and evacuation.