The Samoan Meteorological Service says the effects of Cyclone Olaf should be felt later tonight.
The Director of the Service Mulipola Ause'etaria says Olaf has been intensifying over night with winds of 130 kilometres an hour in the centre, gusting up to 160 kilometres per hour.
Mr Ause'etaria says the country is currently in Storm Watch mode but he expects an upgrading to Hurricane Warning mode shortly.
He says his service has been warning locals to prepare.
"Since last night it was about 255 nautical miles north west of Savai'i island, and it's expected to be at 10pm tonight, around about 150 miles, so we could be affected by the gale force winds by sometime tonight."
Meanwhile, cyclone Nancy, which is currently between the northern Cook Islands of Suwarrow and Palmerston, is continuing on a south-easterly path and is expected lie about 110 kilometres north of Aitutaki in the early hours of tomorrow morning.