A tropical depression (TD06F) has been upgraded to category 1 Tropical Cyclone Nat near the Cook Islands.
In its latest special weather bulletin at 8.40am New Zealand time, Fiji's Meteorological Service said Tropical Cyclone Nat is moving east southeast at about 15 knots
The weather office has issued a nautical gale warning in relation to the storm.
An alert is in place for the Southern Cook Islands.
Fiji Metservice says the storm is set to bring sustained winds close to the centre of around 83 kilometres per hour and gusts between 90 to 120kph.
The cyclone is tracking to remain in the north of the Southern Cook Islands area and stay at sea.
Palmerston, Aitutaki and Mauke are expected to be the most effected islands.
Emergency Management Cook Islands director John Strickland said the country is prepared for Tropical Cyclone Nat.
"The Cook Islands is always resilient, we are always prepared," he told RNZ Pacific.
"As we speak, messages to the Pa Enua (outer islands) are being relayed keeping everybody updated…we are very much prepared."
At the moment it is calm in the Southern group, Strickland said, adding but the Northern group will be experiencing strong winds and rough seas.
He said the disaster management office was working closely with Fiji's Metservice.
'Bring isolated damage to trees or homes'
Earlier on Tuesday morning, Fiji Metservice senior scientific officer Iosefa Cauravouvinaka told RNZ Pacific the cyclone would not surpass category 1 strength - the weakest cyclone category.
"As it moves into the [Southern] Group it moves into an unfavourable area of cooler water as it moves into the south," he said.
He said if the the cyclone intensifies it will be just the high end of a category 1 cyclone.
Cauravouvinaka said the cyclone is expected to bring isolated damage to trees or homes with light materials.
"Those communities along the coast might be most affected."
He said the cyclone may only have a minimal impact.