Two point eight million South Sudanese remain in urgent need of food assistance, UN agencies warn.
At least 40,000 people are on the brink of catastrophe, the agencies add.
UN stresses worries that there is an increase in hunger during the post-harvest period.
The UN agencies noted that the dry season could bring additional hardship to people facing the most severe levels of hunger.
Displaced people in Unity State, who have been living on fish and water lilies to survive, are running out of their only remaining sources of food due to no flow of water, UN warns.
Unless humanitarian assistance can reliably reach them during the dry season, they face catastrophe in the coming months, they add.
The UN agencies call for a speedy implementation of the peace agreement and unrestricted access to conflict areas to deliver supplies.