It would be really good to have a temperature readout in the web interface somewhere with the advent of the pi 4.
Currently I have pi-hole co-installed and that gives it to me and I found vcgencmd in /opt/vc/bin so that helps.
I am running the pi 4 without a case, heatsinks installed and a pifi DAC+ hat and it runs at 34C with a fan blowing in from the card end.
Without it it runs around 44C, I think a case would make this higher plus I am in Australia and its in the middle of winter at the moment.
Max air temp at the moment is around 23C not 30C+
Running Kodi with Netflix on the pi4 resulted in 80C+ and crashing so this iteration is heat sensitive and it is recommended to have a fan
I have another post here on running runeaudio on the pi4 which has photos of my system. Amazingly the sound seems louder and clearer,
Don't know whether I am imagining that or not.