It's normal for your HD to heat up when processing a lot of data. But if your Mac’s hard drive is constantly working above 115°F, there’s probably something wrong with it, especially if you can also hear the fans working louder.
That’s why it is important to keep your hard drive from overheating - you don’t really want it to fail unexpectedly.
Don’t place your MacBook on your lap or on a blanket
That’s because you might accidentally be blocking the fan from working properly and the disk needs the airflow to cool down.
Keep your room clean
Dust is one of the HD's worst enemies because it doesn't only draw in air, it draws in the dust, too. Eventually, the dust accumulates and makes it difficult for the fans to work.
Avoid external heat
Try not use your MacBook for long periods of time when the temperature in the room is above 95°F (35ºC) since the disk (and computer) will also heat up. Do not place your computer between different devices, like your TV or routers - basically any devices that themselves can heat up.
Do not run many apps in the background
Running too many applications at once takes up too many resources.
Those are some basic tips on how to cool down the temperature on your Mac's HD.