Local and international NGOs are working with the National Emergency Management Office (NEMO) to try and gauge the extent of the damage on the main island of Tongatapu, which hosts the capital Nuku'alofa and the nearby island of Eua.
On Tongatapu, the category four cyclone brought winds of over 233km/h, which ripped roofs off houses, brought down trees, destroyed a Catholic church, and took the Tongan Met Office and the national radio station off line.
Tonga's Red Cross said the level of damage to crops, homes, vegetation and infrastructure was extremely high following the cyclone.
Spokesperson Polikalepo Kefu said three teams from the Red Cross had been assessing different areas of Tonga and information was still being collated.
He said some people were still in evacuation centres but many had returned to their homes to assess damage and begin repairs to their rooves.
There had been a few people with injuries taken to hospital from 'Eua Island but he has not heard confirmation of any deaths, Mr Kefu said.
Many people were shocked and traumatised by the scale of last night's weather, he said.
"The scene in Nukualofa is very devastated. From experience talking to people, the people are still living in, they still can't believe that this is Cat 5, this is Category 5, Cat 5 and you can see fallen trees and even fallen houses, and they are still in a mess."
Polikalepo Kefu said it was vital for people to begin repairs and try to clear up excess water to avoid an escalation of the dengue fever outbreak with the potential for mosquitos to breed in pooling rain water.
Meanwhile, former government minister in Tonga said almost all the crops on the island of 'Eua had been destroyed due the cyclone.
The category four storm went almost directly over 'Eua which lies just south east of the main island of Tongatapu.
Former 'Eua MP Sunia Fili said the storm had dealt a huge blow to the local agricultural sector.
"The kava, the cassava and yam too, all the crops near town. Also the breadfruit around in town and the town hall was down and also many small houses. Only the new houses was good but many families are in a very bad situation."
Sunia Fili said he had never experienced a storm of such intensity.