Non-government organisations working with the Tongan government have formulated a Cyclone Ian response plan, which is expected to be made official today.
Greg Grimsich of the United Nations Office for the Coordination of Humanitarian Affairs says the plan brings together the various assessments made since the category five storm struck more than two weeks ago.
He says it highlights where aid is needed in water sanitation, safety, shelter and food.
"What we are doing with this response plan is just basically pulling together a more coherent picture, because there have been a number of different assessments that partners have conducted and it's just a bit more indepth analysis of that, in honing down on the priority areas that need to be addressed - like shelter, where there are outstanding gaps, and clean drinking water, and emergency food as well."
Greg Grimsich says Ha'apai was in a drought before the cyclone and according to the Met Service is likely to continue to be for another four months.
He says the response plan will outline the best way to deal with that.