Tropical Cyclone Donna has strengthened to a category 3 storm as it approaches Vanuatu's north.
People in Torba and Penama provinces have been told to act now with Cyclone Donna forecast to make landfall this evening.
The yellow alert has been raised in those provinces, requiring everyone to find shelter.
The blue alert is in force further south and west, in Sanma and Malampa provinces.
The authorities are warning people there to prepare by securing their homes and valuables, cutting down dangerous trees, organising food and water, and having torches, charged phones and an evacuation kit ready.
Donna is a Category 3 storm and destructive storm-force winds of up to 185km/h can be expected in Torba and Penama in the next 12 hours.
Winds of up to 130km/h are forecast in Sanma and Malampa in the next 12 to 24 hours.
At 5pm local time the cyclone was about 160km north northeast of Vanua Lava in Torba, Vanuatu's northernmost province.
It was moving in a west northwest direction at 13km/h.
It will also bring heavy rain with flash flooding expected in low lying areas and close to river banks.
Phenomenal seas with swells of up to six metres are predicted in Torba, Penama, Samba and Malampa.
Duty forecaster Levu Antfalo said people needed to take all the necessary precautions.
"Our director had a meeting with the national disaster office and we have had stakeholders do preparations on their part," Mr Antfalo said.
"We have issued warnings and sms [short message service] since yesterday."
Shipping and tourism operators prepare for Donna
Vanuatu port authorities are reviewing operations in light of the cyclone.
Several ships have already decided not to berth in Port Vila for safety reasons.
The chairman of Port Vila Cruise Tourism, John Tonner, said he was hoping the storm did not get worse, as it could start to impact on food and other supplies.
"It's affected us across the spread, from tourism vessels as well as the gas and fuel tankers, with a few container vessels have had to reroute to get around Cyclone Donna, and she is still a little ways away yet, but her impact is still far reaching, even now," he said.
Mr Tonner said it was lucky that no ships were on track for the northern Luganville port.
An accommodation owner in the Banks Islands, Florence McKenzie, was warning neighbouring villagers and guests and taking her own precautions.
"We prepare our food and get coconut leaves and put it on the house just to block it from the wind," Ms McKenzie said.
"Now it's raining and [there's] a bit of wind.
"While I am used to cyclone, I am just worrying - as I have guest with me in my bungalow, so I am trying my best to protect him," he said.
Ms McKenzie said she would relocate to a concrete house in the village, should the rain and wind gusts intensify further.
Fiji's Meteorological Service latest update can be found here.
RNZI's AM service is now on for listeners in Vanuatu - tune in to 9700 kHz in the 31-metre band for updates on Cyclone Donna.