(see High temperature indicated on Pi4 for details)
It would be good to have the "red fire icon" (warning) threshold for the temperature shown on the admin webinterface a configurable setting.
Otherwise this visualization might be useless (e. g. on a Pi 4 without case and without cooling the normal temperature is around 63 degrees and therefore always in the "warning state" on the pi-hole webinterface).
Would a variable level based in architecture be useful? The Pi Zero is typically in the 30's C, for example.
We currently have the hard-coded limit of 60°C as also already mentioned elsewhere by @jfb.
This has last been changed in 2016
https://github.com/pi-hole/AdminLTE/pull/293
but I agree that a user-definable setting (or even better a architecture-dependent value) seems best suited. I'm willing to implement this if nobody beats me to it (I'm on a long business trip for two more weeks at the moment).
This was actually a very quick one, see
You can set the desired limit by adding
TEMPERATURE_LIMIT=63
in your /etc/pihole/setupVars.conf file. Note that the limit has to be specified in Celsius, regardless of the unit you selected for displaying.
Not sure if you need to invest time making it arch dependent if too difficult.
Most CPU's that I know of ARM/Intel/AMD get fried above 90 Celsius.
And the thermal paste or pad vaporized.
Talking from experience with the whole IBM X server's, Thinkpad, POS range of products and countless SBC's 
I agree, user-definable is the first step. We can change the hard-coded default value very easily in a follow-up PR.
Thanks for this information. It useful
Implemented.