Hawaii officials urged residents and visitors to be prepared as a strong tropical storm approached the island state.

Olivia was a few hundred miles east of Hilo late Monday with maximum sustained winds of 70 mph (115 kph). It was downgraded from a hurricane earlier in the day after wind shear weakened the storm.

Honolulu Mayor Kirk Caldwell cautioned against complacency, noting tropical storms have led to flooding in Honolulu in recent years.

"We don't know what it's going to look like as Olivia approaches the Hawaiian Islands. So please, folks, don't let your guard down," Caldwell said.

He said crews were working hard to clear debris from streams so they wouldn't block expected increased water flows.

Forecasters say Olivia may drop 10 to 15 inches (25 to 38 centimeters) of rain on the Big Island and Maui County, though some areas could get 20 inches (50 centimeters.)

Wil Okabe, Hawaii County managing director, said work crews were being sent to neighborhoods and parts of highways that flooded and suffered landslides during Hurricane Lane last month.

"By having people around to monitor the situation, to look for the signs, we can respond much quicker," Okabe said. The county is also preparing to open shelters.

Lane dumped more than 52 inches of rain on the Big Island, marking the nation's second-highest rainfall total for a tropical cyclone since 1950. Nearly 40 people had to be rescued from floodwaters, while about 200 people reported damage to their homes on the Big Island because of Lane.

Hurricane Harvey, which deposited more than 60 inches of rain in Texas last year, is the nation's wettest tropical cyclone in the past seven decades.

The ground has dried since Lane so there isn't concern about it being already saturated before the Olivia arrives, Okabe said.

Keith Regan, managing director of Maui County, urged visitors to stay away from the town of Hana and the narrow winding road leading there. Hana Highway is a popular route for tourists to the island and could suffer some of the biggest effects of the storm.

Hawaii Gov. David Ige says the state would be placing road equipment in Hana before the storm arrives so crews will be ready to respond if the highway gets blocked.

Oahu and Kauai are forecast to receive 3 to 6 inches (7 to 15 centimeters) of rain, though precipitation could be as much as 8 to 10 inches (20 to 25 centimeters) in some areas.

The forecast showed the center of the storm heading for Maui. But officials stressed there's uncertainty about the storm's exact path.

"It's important that we don't focus on the forecast track. This storm could directly impact every area of the state from South Point all the way to the north shore of Kauai," said Tom Travis, the administrator of the Hawaii Emergency Management Agency.

On Guam, residents woke up Tuesday to flooded streets, downed trees and widespread power outages after Typhoon Mangkhut passed through overnight.

The Pacific Daily News reports government agencies were conducting damage assessments and beginning to clear roads. About 80 percent of the U.S. territory was without power.

Hurricanes are spawned east of the international date line. Typhoons develop west of the line.