Erick, rated a Category 1 hurricane, is the season's third hurricane and potentially could grow to a Category 3, but is expected to weaken again before reaching Hawaii.
Tropical Storm Erick grew into a hurricane on Monday in the eastern Pacific, packing maximum sustained winds of 120 km/h as it churns more than 1,610 km from Hawaii's Big Island, and is expected to get stronger, forecasters said.
The season's third hurricane, Erick is rated Category 1 on the Saffir-Simpson hurricane wind scale and could reach category 3, with sustained winds of more than 178 km/h in the next two days, the National Hurricane Center in Miami said.
"A weakening trend is expected to begin later in the week," it said in an advisory.
The weather system is expected to weaken back into a tropical storm by the time it makes its closest approach to Hawaii, and is forecast to skirt south of the Big Island on Friday morning.
Forecasts call for a higher chance of gale-force winds from the storm on the Big Island later this week.
Another tropical storm, Flossie, was trailing Erick farther out in the eastern Pacific.