While a comment above states there’s a study [3] showing no correlation, it’s difficult to understand how–when the A/C failed at two buildings–we lost several drives; first those in external enclosures, then those in machines where the fans were failing…in more than one event and at different times of the year.
Another comment states an energy conservation rule–what goes in must come out–and makes a sweeping generalization concerning heat transfer. Unfortunately, this is entirely incorrect; one must take into account the energy required to create magnetic moments, lateral head translation, and excess energy that travels through the system (relatively) unhindered. To wit, energy loss through components that generate it either through resistance, friction, or by virtue of simply failing to be a superconductor is a small part of what’s happening. If energy out (as heat) was the same as electrical energy in, the device wouldn’t function.
Finally, friction. In a hard drive, heads FLOAT a small distance from the platters. Someone else said it best, in 1974:
The engineering requirement for a computer magnetic read-write head is similar to flying a Boeing 747 jet airliner at full throttle a few inches above the ground. [1] – Donald Zipperian, CTO, Pace Technologies, Tuscon, AZ
In 2007, the 747 has to fly at 0.01–with 100,000 passengers [2]–but it’s still not touching the platters! If they do, your heads crash and the drive–platters spinning 5-10K/second–will shear off metal particles, flinging them all over a landscape that’s supposed to be clean and flat. As for the study, IT DID find negative effects over 104F (40C). When metal gets hot it EXPANDS, and there is NO guarantee that it will expand evenly, within the tolerance of the counter-force exerted by mechanical constructs such as compression springs or leaves, OR that the heads will remain in the same position in 3D space, resulting in data errors.
Finally, if you heat up a (ferro) magnet, it dies [4]. These temperatures are high [5], but it’s useful info in case of fire.
Sources:
[1] http://www.nsf.gov/news/news_summ.jsp?cntn_id=100367
[2] http://www.magneticsmagazine.com/images/Presentations/2007/Goglia.pdf
[3] http://www.pcworld.com/article/129420/high_heat_may_not_harm_hard_drives.html
[4] http://www.physlink.com/Education/AskExperts/ae472.cfm
[5] http://www.tomshardware.com/reviews/raid-recovery,1542-3.html
and http://www.ocforums.com/archive/index.php/t-454159.html
and http://www.priorartdatabase.com/IPCOM/000111895
If a disk fails, just take it out, send it to the manufacturer, who cares.