Question: I have a radeon hd 6670, and I have overclocked the GPU clock to 850 MHz and the memory clock to 1040 MHz. I then ran Diablo 3 with SpeedFan running in the background to check the heat of the GPU, and it was at 53 degrees Celsius. This doesn't seem to be too bad, but there was a flame icon next to this temperature in the SpeedFan app. How hot is too hot for a graphics card?

If this is too hot, should I not overclock it or just install more case fans too keep it cool?

Answer: 
GPU's can withstand temperatures close to 100C for extended periods, and anything below 75C is safe. 53C is a very good load temperature. Note however that many tools like Speedfan only report one sensor reading from the GPU, and other sections of your card might be up to 10C hotter - but you're still in the green.

I have a HD6950 at 840MHz/1325MHz and it peaks around 55C on full load with moderate fan activity, for what it's worth.
There are already several answers here on superuser on questions about the temperature ranges for GPUs. Compare this answer for a [Radeon HD 6870](https://superuser.com/a/374296/65379) for example.

The SpeedFan Icon only warns you at a predefined value that is safe for most GPUs. This value does not reflect actual temperature ranges in any way. It should be possible to change the value yourself.

Check the [Speedfan Article](http://www.almico.com/sfarticle.php?id=5)

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> The TEMPERATURES tab allows to define a warning level for each temperature. 
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