More than 1 million people in Hawaii are already seeing the first signs of Hurricane Lane, a Category 4 cyclone that could become the first major hurricane to make landfall there in 26 years.
The storm is moving closer to the Hawaiian islands with sustained winds of 130 mph, and forecasters say its dangerous center will move very close to the islands or make landfall Thursday through Friday. It could be so devastating that authorities are urging residents to set aside two weeks' worth of food and water.
"Be prepared to shelter in place with 14 days of food supplies and water and any other necessities," Hawaii Gov. David Ige said at a news conference Wednesday.
Landslides are a concern, with 10-30 inches of rain forecast through the weekend -- and slides already were happening on the Big Island as the storm's outer bands hit Thursday morning.
On the Big Island's northern tip, landslides were blocking parts of Route 19, the county civil defense agency said.
Buses around Honolulu have been picking up residents in need and taking them to shelters. All public schools canceled classes until further notice, and many state employees have been asked to stay home.
The storm was in the Pacific about 230 miles south-southwest of the Big Island town of Kailua-Kona early Thursday.
Tropical storm force winds (39-73 mph) stretch out to 140 miles, so even if the hurricane doesn't make landfall, it could have widespread impact. Lane threatens to bring dangerous winds, landslides, rough surf and major flooding.
All of the islands are under weather alerts.
A hurricane warning is in effect for the Big Island as well as Maui County and Oahu -- meaning hurricane conditions are expected there. Kauai and Niihau are under a hurricane watch, meaning hurricane conditions are possible and that winds of at least 39 mph are anticipated in the comings days.
Why is Hurricane Lane so rare?
The Central Pacific gets few hurricanes and tropical storms. The Atlantic or Eastern Pacific usually see many more named storms.
Hawaii is a small target in a vast ocean and isn't often threatened. Hawaii gets a named storm within 60 miles of its coastline about once every four years on average, forecasters say.
Lane could become a further rarity if its center crosses land. Only two hurricanes have made landfall in Hawaii since the 1950s: Hurricane Dot in 1959, and Hurricane Iniki in 1992.
How are people reacting?
People have been rushing to stores for supplies and are stocking up on canned foods, ramen, water and toilet paper.
Some were going for plywood to board their windows and for generators. Others have been filling up propane tanks and waiting in lines that circle around the block to get gas for their cars.
"(I'm) filling up my bathtub with some water, hoping to board up my main windows in time," a shopper on the Big Island, Shana Bartolome, told CNN affiliate KHON on Tuesday.
Authorities are asking people to seek shelter before it's too late or to stay in their homes if they believe those structures can withstand hurricane winds.
Many others are leaving. Long lines were seen at airports in Honolulu as hundreds of people tried to catch flights out of the islands before the storm comes closer.
The 15 airports throughout the state will remain open as long they don't suffer damage to their infrastructure or the debris "makes flight operations unsafe," the Hawaii Department of Transportation said in a statement.
President Donald Trump approved a disaster declaration for Hawaii on Wednesday ahead of the storm.
In a statement announcing Trump's approval, Gov. David Ige said Hawaii had submitted the request for a Presidential Major Disaster Declaration to help with the impact the hurricane may have in the islands.
"The approval of the Presidential Disaster Declaration means that Hawai'i will have quick and efficient access to federal resources in the wake of Hurricane Lane, as our communities and residents recover from any damage and losses caused by the storm. We are grateful to the president and FEMA for the swift approval of our request as our state braces for the severe weather ahead," the governor said.
What are experts saying?
Tropical-storm-force winds -- 39-73 mph -- and rain could be seen on portions of the Big Island and Maui County on Thursday, the Central Pacific Hurricane Center said.
As Hurricane Lane's outer bands approach the islands, steady and heavy rain could lead to major flash flooding. Most areas are expected to see 10 to 20 inches through Sunday, while some could get more than 30 inches.
Over 8 inches of rain was reported Wednesday on the Big Island, the National Weather Service office in Honolulu said.
Another important threat is storm surge.
"The combination of a dangerous storm surge and large breaking waves will raise water levels by as much as 2 to 4 feet above normal tide levels along south and west facing shores near the center of Lane," the hurricane center said.
The surge will be accompanied by large and destructive waves.
While the exact path of Lane remains uncertain, CNN meteorologist Pedram Javaheri says the storm could weaken as it nears the islands. Conditions could trigger a weakening of Lane in the coming days, but it would still be dangerous because it's likely to remain a Category 1 cyclone.