What exactly is System temp?

[spongeguar]

So for the longest time, I had thought 'System temp" to be the ambient temperature inside my case.
I noticed it was at 36c today, so I stuck my hand behind my case, it was NOT 36c. more like 21-25c.
I played some games, noticed it went up to around 50c(cpu temp was 43c). It dissipated within about 5-10 mins, so again, I doubt it was ambient temp.

Then I checked bios - Indeed, my CPU is running a good 3-10c colder than my "System temp"

So what's the culprit here? Is my system temp sensor not ambient case temp? Is it a bad sensor?
Is my CPU sensor bad?

Confused is me.

EDIT: Also, for what it's worth, my case has a vent near the cpu with a circular metal thing that leads the air directly into the CPU. Could this be the cause?

 

[WR2]

More than likely something on your motherboard is getting warm.
You'd need to know where your motherboards system temp probe is located to figure out more.

 

[spongeguar]

More than likely something on your motherboard is getting warm.
You'd need to know where your motherboards system temp probe is located to figure out more.

It's a ga-ma790GPT-UD3h if this helps anyone.

 

[hunter315]

What program are you using to monitor your temperatures? If it is consistently slightly warmer than your CPU i would say your two options are that its your northbridge temp or its the CPU socket temp.

 

[spongeguar]

What program are you using to monitor your temperatures? If it is consistently slightly warmer than your CPU i would say your two options are that its your northbridge temp or its the CPU socket temp.

I've used open hardware monitor, HWmonitor, and my bios.

 

[roonj]

System temp is the motherboard temperature, it may be taken at PWM or Chipset or anyplace the manufacturer chose to put the sensor.