The El Nino has caused severe drought through much of the region including Vanuatu which is still recovering from Cyclone Pam.
UNICEF Pacific Representative Karen Allen says affected children are showing signs of malnutrition and diarrhoea which could lead to greater developmental issues in the future.
Dr Allen says although governments have said there is no need for any mass appeal, there is a pressing need to look at the potential costs of the system.
"To see that what is available is going to go the distance. So no appeal right now for funds. Many governments had set aside funds, some agencies had money that was still not fully expended from Cyclone Pam for instance, but my prediction is, it's not going to be enough to last us through El Nino."