Tropical cyclone Amos appears to be heading for a direct hit on Samoa's main island, Upolu.
Residents have spent the day stocking up on supplies and securing loose items as the storm is intensifying and is expected to develop into a severe category four storm.
The Fiji Meteorological Service, responsible for tracking the region's cyclones, says Amos is likely to pass across the top of Savai'i, before veering south and crossing Upolu, near the capital, Apia.
The category three system, with winds in excess of 160km/h, is still more than 300 kilometres away from Samoa, but forecasters say it is continuing to intensify and is likely to be a category four tonight.
Samoa's Meteorological Service says the country should start to experience heavy rain, strong winds and rough seas from this afternoon.
It says the cyclone poses a serious threat to the country and people should be prepared.