Aid workers are moving to get roofs back on houses on the cyclone-hit islands of Pukapuka and Nassau in the northern Cooks.
Ships are transporting water supplies and purification tools to the islands but residents fear running dry in between shipments.
The NZAID manager for disaster response, Chris Day, says reroofed houses will help make the water supply steadier.
"Their main source of water supply is catchment, so catchment on, from the roofs. At the moment what we need to do is ensure that priority is given to reinstating the roofs on the houses that have been affected by the cyclone."
Chris Day says NZAID has made about US$420,000 immediately available to the Cook Islands government for relief efforts in Pukapuka and Nassau.
Ms Day isn't able to say by what time all the funds will be used.
Well the funds are available immediately, and we are working closely with the Cook Islands government and New Zealand, in terms of how to best distribute those funds, so we're very much relying on the ground assessments coming from the Cook Islands government and also the New Zealand High Commission in Rarotonga, and we'll be working closely with them now to ensure those funds are put to best use.