Just for comparison my GPU is sitting at 44°c, it's slightly overclocked @ 685Mhz, 90mm PWM fan is revving away at 50%; but even hitting the cards high spots consistently and repeatedly over a long period never pushes the temps over 55°c.
I do not trust onboard hardware temperature sensors to be accurately calibrated, nor correctly managed in many cases. If in doubt see if you can manage to burn your fingers (power down, earth yourself too...) or better still, beg, borrow, or steal, a decent techies temperature probe...