Checking your computer component temperatures once in a while is recommended. Knowing whether your coolers work efficently enough is important. The temperatures greatly depend on what CPU and GPU you have and under how big load your computer is. Your current environmental temperatures can also affect your hardware by ~5°.
Normal temperatures for your hardware ( CPU and GPU )
Desktop ~40°C ( 104°F )Laptop ~50°C ( 122°F )
Under Heavy Load
Desktop ~60°C ( 140°F )
Laptop ~70°C ( 158°F )
Over 70°C ( 158°F ) is already too much heat and it can destroy your hardware in a long term. Check here how to prevent your laptop from overheating.
Some motherboards allow you to monitor your temperatures in BIOS, but there are also third party softwares that allow you to do that. Most of them have many other features such as clocking, system information, etc. Some examples below.
PC Wizard (get it here)
Speedfan (get it here)
Everest (get it here)