The alert status of Agung was raised to the highest possible level on Friday evening, following a spike in seismic activity.
It is among more than 120 active volcanoes in Indonesia.
"Even with all the signs and calculation we have today no one can tell when is the eruption will occur", said Surono, an expert of volcanology and former head of Indonesia Volcanology and Geological Disaster Mitigation Center.
"Agung volcano is said to be close to erupting and the Bali island just shaken by a M4.2 natural disaster".
Mount Agung is seen from a nearby village in Karangasem, Bali, Indonesia, 24 September 2017.
Evacuees are now living in temporary shelters: sports centres, village halls or even with relatives or friends.
The government has set up 238 evacuation points for villagers and 14 tonnes of aid has been flown in, including tents, blankets, mattresses and communications devices. However, it was 10 times smaller than Mount Agung's 1963 eruption.
"We have already sold our cattle, because we thought it was better than leaving them there for nothing", he said.
"The mountain has not erupted until now".
Authorities have urged people to stay out the danger zone, a designated five to seven-mile radius of the volcano. The volcanology agency is also drawing data from Global Positioning System and satellite imagery, and everything seems to indicate the same thing: while it can't be said for sure that the volcano will erupt, there is every reason to believe that the volcano will probably erupt.
The 3,031-meter (9,944-foot) mountain hurled ash as high as 20 kilometers (12 miles), according to volcanologists, and remained active for about a year. Lava traveled 4.7 miles and ash reached Jakarta, about 620 miles away.
A view of Bali's Mount Agung on September 25.
A spokesman from the Association of British Travel Agents (ABTA) said: "The Indonesian authorities have kept the alert level at the highest classification, meaning an eruption could be imminent". "Otherwise, our farms would not be able to be planted again".
President Joko Widodo was expected to visit evacuation centres on Bali later on Tuesday.