The thermal throttling point on recent Intel chips is somewhere between 90 and 100 C. In that range, the CPU will start downclocking itself dynamically in order to maintain what it feels to be acceptable clocks with a maximum percentage of time spent at an overheated temperature. Its goal is to stay below 90 C, and it'll do that if possible.
You start to see dramatic clock drops if it spends too much time at 100 C, past which it will not allow itself to gain heat. If it spends too long at 100 C or manages to go significantly over that it'll shut down.
You cannot change this behaviour, and I highly stress that you should not attempt to circumvent it or run a process or above 85 C for any significant period of time. Go buy a $100 all-in-one closed loop liquid cooler and some decent thermal paste and you'll be able to run your system at a more than acceptable overclock for minimal mess without screwing with your thermals or requiring exotic cooling solutions.
Note that while you can't (and shouldn't) change this behaviour; it's possible (and likely desirable) for an OS to take it into account. This could include keeping track of how quickly CPU temperature increases under load, and using this information to detect when CPU temperature is increasing at an abnormal rate and alert the user/admin of "suspected CPU fan/cooling system failure".
It can also include shifting CPU load to other CPUs if one is hotter than the others, and downclocking CPUs when running lower priority tasks; to reduce the chance of the CPU doing thermal throttling when you're running high priority tasks, and so that (when it's unavoidable) the transition is a more gradual "everything fast" to "some things slower" to "everything slower" (rather than an unexpected and sudden "everything fast" to "everything slower" change).
Also note that (for OS power management) things like fan speed/fan noise and (laptop or UPS) battery level are involved too, and CPU speed is just one factor in the OS's "performance vs. power consumption vs. fan noise" compromise. It's not as simple as "let's always try to do everything as fast as possible".