The Fiji Met Service says Category four Winston has turned back towards Tonga after passing through the northern islands earlier this week.
On its current path the storm is moving away from Niue and back between Vava'u and Nuiatoputapu, with Fiji expecting to feel its brunt again in the weekend.
The storm's average wind speed is up to 165 kilometres an hour and gusting to 230.
Met director Ravind Kumar says Winston will be closest to Vava'u tonight and could possibly be a category five storm by then.
"We can just imagine how strong those winds can be, especially with the category four, category five systems. It has a potential to blow out the well-structured, well framed homes, uproot trees as well as the seas can be very phenomenal."
Disaster Management authorities in Tonga are currently meeting, while local police report at least 63 families in Vava'u and 35 families in Ha'apai are already in shelters.