UNO operating temperature

my UNO stops communicating when the temperature is above 38-40C. is this normal? works below 36C.
Rest of the circuit is working at 48C (my current outside temperature).
Not sure if it's a CPU or USB chip problem. the board is several years old.

How are you powering it?

Are you powering any other parts of your circuit from the 5V pin? If so, how much current does it draw?

USB power

Yes, the circuit draws 5 to 6 ma at ambient (29C) and 40C

heated the uno with the 5v supply isolated from the heat seems to work, guessing one of the large capacitors doesn't like the heat (shorts). I have had the the same problem with other power supplies.
will try another uno, but the 18b20's I was testing are also starting to fail above 45C, so I need to find a better source for them first.

Thanks for the quick response.

OK, I was checking because the situation is different if the board is powered through the voltage regulator via the barrel jack or VIN. The linear voltage regulator has a thermal shutdown feature.

But if you're powering the board via the USB then the 5 V voltage regulator is not used. the 3.3 V still is, but only to supply whatever might be connected to the 3.3V pin.