That's 260 degrees Celsius. Water boils at 100 degrees Celsius (212 degrees Fahrenheit) at sea level.

From the Wikipedia page on the World Sauna Championships, which exposed people to temperatures far lower than the above-advertised '500 Degrees Fahrenheit'.

On 7 August 2010, two competitors were removed from the sauna and brought to the hospital in critical condition after six minutes of 110 °C (230 °F) heat, both suffering from serious burns and trauma. Russian finalist and former third-place finisher Vladimir Ladyzhensky, an amateur wrestler, was dragged out, suffering from convulsions, burns, and blisters. Ladyzhensky died despite resuscitation. Finnish five-time champion Timo Kaukonen was, according to a spectator, able to leave the sauna with assistance. He was reported to suffer from extreme burn injuries and his condition was described as critical but stable.