HONOLULU -- Hurricane Lane strengthened to a Category 5 storm late Tuesday with maximum sustained winds of 160 mph as it moved closer to Hawaii, the National Hurricane Center said. Hawaii County, also known as the Big Island, is under a hurricane warning, meaning hurricane conditions are expected in the next 36 hours.

Oahu and Maui County, which includes the islands of Maui, Lanai, Molokai and Kahoolawe, are under a hurricane watch. A Hurricane Watch means that hurricane conditions are possible within the next 48 hours.

As of 1 a.m. ET, Lane was located about 375 miles south of Kailua-Kona, on the west coast of Big Island, and about 535 miles south of Honolulu. On the forecast track, the storm is expected to move very close to or over the main Hawaiian Islands from Thursday through Saturday. Hurricane-force winds extend outward up to 40 miles from the center and tropical-storm-force winds extend outward up to 140 miles.

A look at the path for Hurricane Lane as seen on Tue., Aug. 21, 2018. National Weather Service / Central Pacific Hurricane Center

Hawaii residents could be slammed with heavy rain, flash flooding and high surf even if the center doesn't reach the islands, said senior Honolulu forecaster Tom Birchard.

Get Breaking News Delivered to Your Inbox

Officials have urged residents to prepare "for the worst," CBS Honolulu affiliate KGMB-TV reported.

"Some people might say, 'Another hurricane, it didn't hit us last time, we don't need to worry.' No, we got to plan for the worst and hope for the best," Honolulu Mayor Kirk Caldwell said on Monday.

Officials are also taking steps to prevent problems, including closing beach parks and clearing streams, KGMB-TV reported.

CBS affiliate KMGB in Hawaii