its 75F in the office. A/C is on.
The PI4B 2gig is on my desk
cpu speed is currently 600mhz
top says between .9 and 1.2
so the cpu is IDLE.
with case stock PI4B case installed, lid on, and idle its: 159.8F
if i open up chromium youtube.com with the case on the FUll HIGH TEMP ICON Displays in the upper corner.
goes up past 185F
with chromium playing a video in youtube.com
w/o case sitting on desk.
The Card included with the PI4B shows an INFOGRAPHIC showing not to cover/contain the PI4B board, installing it inside its case kind of go's against this recommendation.
My suggestion is to (at least) include a small fan and some venting with the PI4B case. just slide on -/+ onto the 5v of the gpio to power fan.