Quote taken from
http://www.heatsink-guide.com/content.php?content=hdd.sh tml
"Most recent IDE hard drives come with internal temperature sensors, and are capable of reporting their operating temperature via SMART; software utilities are available for displaying the temperature of your hard drive. This temperature readout is not very precise, but definitely good enough to give you a hint whether your drive is running too hot or not. Consult the website of your hard drive manufacturer to learn about the maximum operating temperature of your hard drive. Typical maximum temperature range is 50-55�C, with some drives being able to operate at up to 60�C."
If you insist on using Fahrenheit (why?), 50C = 122 deg F, 55C = 131 deg F, 60C = 140 deg F.
Chris