The Tonga Red Cross says it has growing concerns for food security and a lack of drinking water as a major drought is expected to continue for the next two months.
On Friday, the Meteorological Service said there was a 70 percent chance El Nino will occur over the next few months, which may mean a drier wet season and more cyclones.
The Red Cross general secretary, Sione Taumoefolau, says it is most concerned about Ha'apai, Tongatapu and 'Eua, where rainfall has been well below normal.
Mr Taumoefolau says the Red Cross has been doing all it can to get clean drinking water to the outer islands.
"The forecast at the moment is not very good. It seems to me the rain will [not] be in Tonga in the next two months or more. Our concern at the moment is drinking water for the Ha'apai area. I think the government, also Red Cross, will be doing our best to provide whatever they can to those people who are staying in the islands."
Sione Taumoefolau is calling on people to use clean water for drinking only.