Ioke quickly began to enter a process of rapid development; strengthening into a hurricane just 24 hours after it had formed. While safely avoiding the Hawaiian Islands, it continued to rapidly intensify and became a major hurricane (Category 3 or greater) on the morning of August 21. Later that day, Ioke intensified even further into a Category 4 hurricane. On August 22, it began to weaken as a result of cooler water and eyewall replacement cycle, and was downgraded back to a Category 2. As a Category 2 storm, Ioke affected Johnston Atoll.