I picked up a RPi 4B the other day to use as a pi-hole[1] and was surprised to see it running at 65C while idling. It doesn't help that I have the board enclosed in the official case, which provides absolutely no airflow.

Everything runs fine at these temperatures, but all of the ports are hot to the touch. Under stress the SoC seems to reach 80C+, which I imagine would make connecting and disconnecting USB devices a fairly unpleasant experience.

[1]: https://pi-hole.net/