A Tropical Cyclone Warning has been issued for all of Samoa.
The country's Meteorological Office says a tropical depression to the northwest of the country has been intensifying and is now a category one cyclone.
The system is about 320 kilometres west of Savai'i and 419 kilometres west of the capital, Apia.
It is slow moving and continues to intensify as it heads closer towards Samoa.
A spokesperson for the office, Luteru Tauvale, says the national emergency office has been activated and there are reports of some low-lying areas being evacuated.
Heavy rain and strong wind warnings have also been issued, with fears of flooding and landslides.
Mr Tauvale says the cyclone is not expected to directly hit Samoa, but wind and rain associated with the system will create many problems.
" In terms of observations from the previous 24 hours the rainfall is well above the threshold of heavy rain. We expect conditions to worsen in the next few hours."
Luteru Tauvale says people should also avoid going out to sea with swells forecast to be as high as 13 to 15 feet.
Storm watch for American Samoa
The US National Weather Service has issued a tropical storm watch for neighbouring American Samoa.
The National Weather Service in Pago Pago says the tropical depression was located about 564 kilometres northwest of the main island, Tutuila, and 682 kilometres northwest of the Manu'a island group.
Forecasters estimate the system will pass about 128 kilometres south of Tutuila late tonight, and 209 kilometres south of Manu'a early tomorrow morning.
Emergency management officials from the local branch of the Department of Homeland Security are advising the public to remain on alert and secure loose items.
Forecasters say a tropical storm watch remains in effect, along with a flash flood watch. It also added a Gale Warning for the territory's coastal waters.
Warnings issued for Tonga
The Fua'amotu tropical cyclone centre has issued a tropical cyclone advisory for the Kingdom, which lies not far to the south of Samoa.
It says the tropical depression was about 315 kilometres north of Niuafo'ou at 1am local time, moving east-southeast at 20 kilometres per hour, and slowly intensifying.