Some signs your GPU is overheating inside your PC
You don't need monitoring software if you look for these signs

Although most modern graphics cards have a safe temperature limit of 90C, they shouldn't ideally shouldn't exceed 85C when you're gaming. Otherwise, you'll start experiencing problems. While it's a good idea to keep an eye on your GPU temperature with tools like MSI Afterburner while playing games, the overlay—to me, at least—disrupts the immersion. So, I rarely ever use them unless I'm benchmarking a new game for a few minutes.