Flood victims receive food handouts from the army in Jafarabad district in Pakistan's Baluchistan province on Tuesday. (Rizwan Saeed /Reuters)

Pakistan's flood waters are not expected to recede until the end of August, the country's top meteorologist said Wednesday.

Though the week's forecast does not include heavy rain, existing river torrents were still heading to major cities such as Hyderabad and Sukkur in the south and could yet cause more floods, Arif Mahmood said.

Three weeks of flooding have left more than 20 million people either homeless or otherwise affected.

The scale of the disaster has badly strained the government, the police and army, which are handling much of the relief effort.

At a feeding centre in the city of Jampur, in central Pakistan, 800 people who fled their homes — mostly women and children — are living in about 100 tents. Many of the men are not there because they felt they had no choice but to stay with their sinking and flooding homes elsewhere, military officials told the CBC's Adrienne Arsenault.

Army crews there on Wednesday delivered water and evaporated milk, basic supplies the military realizes will not be enough to feed everyone, Arsenault reported.

"What some of the people say in the camp is that the water has been chasing them," Arsenault said. "They go from one place to another, and then the high water comes to them.

"In some horrible cases, people who have sought high land and climbed trees thinking that would be safer [did so] only to find that the snakes have done precisely the same thing."

1,500 die in flooding

Lack of rain in the forecast should provide some relief for aid agencies who have been unable to reach survivors in areas where the floods and debris have made roads impassable.

At least 1,500 people have died, and tens of thousands of villages submerged, in the flooding, authorities said.

The floods hit first in the northwest, wiping out much of its infrastructure, and then the bloated rivers gushed toward the south and the east, displacing millions more people.

About a fifth of Pakistani territory has been affected.

The UN appealed last week for $459 million US in international aid for immediate relief to Pakistan. On Wednesday, UN spokesman Maurizio Giuliano announced that more than $250 million had arrived.

With files from the CBC's Adrienne Arsenault and The Associated Press