Why is it so hot in Chilean mine?

The Chilean mine is not particularly hot. The average temperature in the San José Mine, where the 33 miners were trapped for 69 days in 2010, was around 32 degrees Celsius (90 degrees Fahrenheit). This is not considered to be particularly hot, especially when compared to other mines in the world. For example, the average temperature in the South African Mponeng Gold Mine is around 35 degrees Celsius (95 degrees Fahrenheit).