Mr Fisi'iahi said his wife would fly to Tonga as soon as she could book a flight.
"I grew up amongst hurricanes and cyclones but this was the worst in 60 years. Water covered almost every house on Tongatapu and Eua, even if they escaped the winds."
His sister is a nurse at the main hospital in Tongatapu and said power cuts forced the burial of nine bodies that would normally be kept in a morgue for up to one week.
Whangarei resident Favava'u Davis said her parents and brother took shelter in a church hall on Monday night after their house was flooded.
She plans to go to Tonga for a weekend to see them.
On Tuesday morning, she said only her father Sione Pasi went back home to check on his two dogs before returning to the evacuation centre.
"Getting in touch with them proved difficult as it was very windy and rainy. They've never been to an evacuation during previous cyclones."