I get this output:

hw.sensors.cpu0.temp0=39.00 degC
hw.sensors.lm1.temp0=45.00 degC
hw.sensors.lm1.temp1=22.00 degC
hw.sensors.lm1.temp2=31.50 degC
hw.sensors.lm1.fan1=2070 RPM

But, I'm rather certain that the third line (22.00 degC) is the actual temp
of the CPU as this is what the BIOS reports as well as other operating
systems (I quad boot this box). This is an under-clocked Intel Celeron cpu
under very little load with good fans, so while low, that temp of 22 degC is
most likely correct. How does OpenBSD gather this temp?

cpu0 at mainbus0: (uniprocessor)
cpu0: Intel(R) Celeron(R) CPU 430 @ 1.80GHz, 907.57 MHz


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Unfortunately we don't know what the BIOS knows.  We don't know what
sensors is where, so you will have to make do.

To find out how OpenBSD gathers this, there have been presentations

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Maybe I'm wrong but it's VERY unlikely that your CPU has the lowest
temperature of all. Moreover, CPU temp is usually the highest available.

"cpu0.temp" AFAIK is read from CPU itself (modern Intel and AMD CPUs have
such sensors). "lm1.*" are read from on-motherboard chip, see lm(4).

So where is your dmesg? And what are other 3 OSes you run? Which software

--
  Best wishes,
    Vadim Zhukov

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It asks the CPU. Of course there's not much documentation, so you  

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