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(CNN) -- Iselle has cleared Hawaii, and all tropical storm warnings have been canceled, the National Weather Service said Friday. It is still a tropical storm, as it drifts farther away from the state.
Hurricane Julio should pass by over the weekend and is expected to track north of Hawaii, according to current predictions, sparing the state. But the weather service advised the public to remain diligent, as weather conditions and the forecast could change.
Iselle's top winds weakened to 60 mph as it made landfall at 2:30 a.m. Friday along the Kau coast of the Big Island.
Had the storm remained a hurricane, it would have been the first to hit Hawaii in decades.
By Friday night, the National Weather Service canceled the tropical storm warnings for Maui County and Oahu. Kauai, however, remained under a tropical storm warning. A warning for Hawaii County was canceled earlier.
A flash flood watch remained in place for the state through 6 a.m. Saturday. Iselle was still producing locally damaging wind gusts over the smaller islands, the statement said.
The state's primary election was expected to take place Saturday despite the storm.
Abercrombie, who has taken advantage of the storm to show leadership and appear on television, is in a tough race against State Sen. David Ige in the Democratic primary. U.S. Sen. Brian Schatz faces a challenge from U.S. Rep. Colleen Hanabusa. Schatz was appointed to the seat after the death of longtime Sen. Daniel Inouye.
Heavy rains were the biggest threat, with general rainfall predicted to be between 4 and 8 inches, although some areas could get more than a foot.
Flash flood warnings cover much of the Big Island, while flash flood watches have been issued for the entire state.
Iselle has already delivered 11 inches of rain on the Big Island, according to Mike Cantin with the National Weather Service.
In a conference call, Cantin said the Big Island should expect more than a foot of rain.
Doug Mayne, of the Hawaii Emergency Management Agency, said heavy rains have prevented the agency from beginning to assess the impact of the storm.
Conditions made it unsafe to get helicopters in the air to access the hardest-hit areas.
Hawaii Electric Light said in a tweet that nearly 22,000 customers were without power in various parts of the Big Island.
As the storm approached, supermarket shelves were swept bare, while schools and government offices closed. Sandbags were placed around homes and hotels, and ports told to close.
In Hawaii County, 630 people have gone to shelters, Mayor Billy Kenoi told CNN affiliate KHON-TV in Honolulu.
The state had prepared for a potentially devastating one-two tropical cyclone punch, starting with Iselle and followed by Hurricane Julio, a Category 3 storm, about 900 miles behind it.
Hurricane Julio could affect the islands over the weekend, though forecasters expect it to brush the state only with its southern outer bands as it passes to the north as a weakened tropical storm.
Julio had strengthened to a Category 3 storm with top winds of 120 mph by Friday morning, when it was centered less than 1,000 miles away.
A relatively rare event
Direct hits are rare for the state. Since the 1950s, two hurricane eyes have hit Hawaii -- and both approached from the south, where water temperature generally is warm enough to sustain the storms' strength.
That's not to say Hawaii hasn't had close calls. The central Pacific sees an average of about five tropical cyclones a year, and some have brushed the state in recent decades.
The cyclones generally approach from the east after forming in the eastern Pacific. But close to Hawaii, dry air, cooler water and wind shear combine to weaken approaching cyclones, dissipating them before they can become a significant threat, CNN meteorologist Indra Petersons said.
Hawaii's most damaging hurricane in recent decades -- Hurricane Iniki of 1992 -- came during an El Nino year, or a year of above-average sea surface temperatures. This year hasn't met the criteria for El Nino, but it could in the weeks ahead, Petersons said.
Iniki killed at least four people and caused about $2 billion in damage when it hit the western Hawaiian island of Kauai, according to the National Oceanic and Atmospheric Administration.
School's out; air travel disrupted
The schools on the Big Island and Maui were closed Friday as residents assessed Iselle's impact.
Some airlines made concessions to customers.
Hawaiian Airlines moved one flight, to Los Angeles, up by five hours to beat Iselle's arrival.
For people who had been scheduled to travel to or from Hawai's airports on Thursday and Friday, United Airlines and Hawaiian Airlines said they won't charge fees to change reservations, and they'll waive differences in fares for those changes.
United canceled flights to Hilo and Kona. American Airlines and US Airways also called off flights out of Kona on Thursday but expected Friday's flight schedule to operate normally.
Island Air will do the same for passengers ticketed from Thursday though Tuesday. Delta Air Lines said it would waive fees for reservation changes for Thursday and Friday, but fare increases could apply. It said two flights had been delayed in leaving the islands.
CNN's Taylor Ward, Mariano Castillo, Katia Hetter, Tina Burnside and Tony Marco contributed to this report.