Although Apple has announced details and features of the upcoming OS, it has yet to announce an official release date.
9 to 5 Mac is saying Apple has asked some of its retail employees to prepare for overnight work on July 24, leading to speculation the new operating system will be available the next day.
The Web site acknowledged the release won't have much to do with Apple's retail stores since Mountain Lion will be distributed via download from the Mac App Store, but speculated the overnight work will see Apple store employees installing the new OS on every Mac computer in the stores.
Mountain Lion, which furthers the design and functional ties between Apple's mobile iOS system and its Mac system, will cost $19.99.
The OS is finished and already distributed in Golden Master form to developers, 9 to 5 Mac said.