In the scorching 40-degree heat of South Sudan, a dark cloud should be a source of relief. But for thousands of people sheltering in the dust of a United Nations base here, the clouds are an omen of looming disaster.
"It's going to rain very soon," warned Charles Riek Wal, who fled to the UN military base last month to escape a wave of killing in Juba. "We need to be rescued."
Rain is one of the greatest nightmares of the aid workers who are trying to save lives in South Sudan. It will turn the dust of this sprawling overcrowded tent camp into a vast ocean of mud, heightening the risk of cholera and other infectious diseases for its 23,000 people.
"The health risks are a ticking time bomb," said Arjan Hehenkamp, general director of the Netherlands branch of Médecins sans Frontières (Doctors Without Borders), who visited the camp this week. "People told me that if it rains in this camp, it will be a disaster."
The rainy season will begin in earnest at the end of March, and a few scattered raindrops have already been felt. Yet almost nobody is returning to their homes. The camp remains huge, with a population density about 10 times greater than that of Mumbai.
The displaced people, largely members of the Nuer ethnicity, are convinced they will be killed if they leave. "People are imprisoned by their own fear," Mr. Hehenkamp said.
With hospitals and markets destroyed and looted, and with the health system in some regions on the verge of collapse, South Sudan will continue to face a humanitarian emergency for months to come, MSF predicts.
In mid-December, at the beginning of the fighting that has killed up to 10,000 people, the UN projected that 400,000 people could be displaced in the first three months of this year. The actual number today is more than twice as high as that projection.
"The humanitarian consequences of the crisis have far outstripped what we thought would be the case," said Toby Lanzer, the UN humanitarian co-ordinator in South Sudan.
"In some respects, we're playing catch-up. This is snowballing. The very sad reality for civilians in South Sudan is that things may get worse before they get better."
If the bloodshed and destruction make it impossible for ordinary South Sudanese to return to their daily farming or fishing activities, the situation could fast deteriorate. "I dread to think what sort of a humanitarian situation we'll be faced with at the end of the rainy season," Mr. Lanzer said.
Outside the capital, the pressures are even greater in some regions. Towns such as Malakal have been subjected to intense fighting, looting, destruction and death. The main hospital in Malakal is littered with waste and sewage, and its compound is filled with displaced families who sought shelter after fleeing their homes, aid workers say.
"I saw people in dire circumstances, short of food, living in conditions with poor sanitation and very little water," said Valerie Amos, the UN emergency relief co-ordinator, who visited Malakal on Tuesday.
"I met women who had walked for days to seek protection and assistance, children who'd been separated from their parents as they fled, and people who said they'd been targeted and abused because of their ethnicity or political affiliation."
Ms. Amos also cited "worrying reports" of interference in humanitarian work, including the killing of three aid workers and a recent incident in which 106 aid workers were prevented from travelling to Juba when they sought safety there.
In order to end the bloodshed and allow people to return home from the overcrowded tent camps, South Sudan will need a genuine reconciliation among its politicians and ethnic groups. But after six weeks of heavy fighting and massacres, reconciliation will be difficult.
The Archbishop of Canterbury, Justin Welby, arrived in Juba on Thursday in an effort to promote healing and peace in the war-torn country. The Archbishop, the head of the world's 80 million Anglicans, said South Sudan's reconciliation must begin with "telling the truth" about the horrors of the past six weeks.
"Face reality," he told South Sudanese in a sermon on Thursday. "Without honesty, there will be no reconciliation. There must be no impunity."