The storm, located off the west coast of Mexico about 730 km west-southwest of Manzanillo at the time it became a hurricane, is expected to strengthen slightly through Saturday before it encounters cooler water and less-favourable atmospheric conditions.
Aletta is the first hurricane of the 2018 season in the eastern Pacific. The hurricane is moving towards the west at a speed of 7 kilometers (5 miles) per hour, which will keep it well away from any land.
"The remarkable intensification of Aletta has continued through this morning", the National Hurricane Center wrote in its 11 a.m. advisory. It boasts a attractive presence on satellite imagery, nearly perfectly symmetric and featuring a well-defined eye.
However, over the weekend, the storm is forecast to steadily decay.
The center said Aletta is likely to become a hurricane by Thursday as it moves westward into the Pacific.
Aletta was first named a hurricane on Thursday, June 7, which is over two weeks earlier than normal.
Centered just under 500 miles south of Mexico's Baja Peninsula, Aletta transformed from a tropical storm into a Category 4 hurricane in just 24 hours.
An average Eastern Pacific hurricane season produces 15 to 16 named storms, with eight to nine becoming hurricanes and four becoming major hurricanes.