Heatsink or metal plate temperatures
These are not scientific, just us noting our experiences as its sometimes useful to know when users will be in contact with heatsink metalwork.
38ºC feels very warm to the touch but is OK to be touching for a period of time..
42ºC feels very warm to the touch. Its not painfully hot or going to burn, but it is pretty warm and would be uncomfortable to touch it for a long period of time.
54ºC is hot but not shockingly so. You can touch it without immediately needing to draw away.
62ºC feels very hot to the touch.