A hurricane that beat the odds was poised to roar across Hawaii on Thursday, blasting the island paradise with heavy rains, damaging winds and hammering surf.

Hurricane Iselle was forecast to become the first hurricane to smash into the islands in more than two decades. A couple of days later, Hurricane Julio could be the second one.

Forecasters had expected Iselle to fall prey to the long trip across the Pacific and the region’s strong upper air flow that is capable of breaking up some of the mightiest storms. But Iselle was unrelenting, so the run on bottled water, milk and toilet paper is in full swing.

“The real effects will probably be felt on the Big Island,” Norman Hui, a National Weather Service meteorologist in Honolulu, told USA TODAY.

“The worst of it will be tonight. This storm is holding together pretty well.”

Not everyone was in a panic, though. The Big Island, the state’s most easterly island, was on track to take the biggest hit.

In Hilo, the island’s biggest city, the skies were overcast but there was no rain Thursday morning. The winds were mild. At one 7-11 in Hilo, a clerk named Lee Anne, 38, said the store has plenty of bottled water.

“I’m kind of skeptical about it,” she said. “We’ve had so many warnings before, but not much has happened.”

Honolulu is on Oahu, a smaller but more populated island that includes Honolulu.

Oahu should avoid the worst of the storm, Hui said. But tropical storm conditions could bring havoc overnight and Friday. Long lines formed at some local stores, and bottled water and other hunker-down items flew off shelves.