Tropical Storm Lala was upgraded to a hurricane on Saturday as it moved toward Hawaii's Big Island, according to the National Hurricane Center.

The storm had maximum sustained winds of about 70 mph Saturday morning, just below the 74 mph threshold required for hurricane classification. 

Forecasters warned that Lala could produce 8 to 12 inches of rain across portions of the islands, with isolated totals reaching 25 inches, raising the risk of flash flooding and mudslides.

Strong winds were already affecting the Big Island and Maui, particularly at higher elevations. Dangerous surf, powerful rip currents and possible coastal flooding were also expected, with storm surge potentially reaching 3 feet in some areas, the Weather Channel reported.

The National Hurricane Center said the system was expected to pass near the island Saturday before tracking south of the smaller Hawaiian islands Sunday. Forecasters anticipate some weakening after the storm encounters the Big Island's mountainous terrain.

Hawaii Gov. Josh Green declared a state of emergency and urged residents to take the storm seriously. 

The potential impact is particularly significant because the Big Island has not experienced a direct hurricane landfall in more than a century.

Officials have opened shelters and canceled some events as residents prepare for flooding, power outages, landslides and hazardous ocean conditions. Authorities are urging people to remain indoors during the worst conditions and stay away from beaches and floodwaters.