Hawaiian authorities sounded alarms across the island on early Saturday morning, and are evacuating 100,000 residents and tourists.
A tsunami warning, which is the highest alert level, follows a massive 8.8 magnitude earthquake off Chile which sent waves across the Pacific Ocean.
The possible tsunami is estimated to first arrive at about 11:19 a.m Saturday local time (4:19 p.m. EST).
The sirens sounded at 6 a.m. local time (11 a.m. EST) to warn of a potential tsunami triggered by the earthquake, which killed at least 148 people.
Hawaii's state department of Civil Defense said authorities were expecting to evacuate more than 100,000 people in long-designated tsunami zones before the waves hit.
The danger could last for hours, because the first wave is not necessarily the worst, said spokesperson Shelly Ichishita, according to Los Angeles Times.
We are taking this very seriously.
The Pacific Tsunami Warning Center issued a Pacific-wide warning.
President Barack Obama urged West Coast residents to be prepare themselves for the possibility of dangerous waves and currents.
Obama also encouraged Hawaii, American Samoa and Guam to follow the instructions of their local civil defense team.
Watch live streaming of the tsunami here.