High end CPUs can often dissipate 130W when stressed under normal operation – and considerably more when over-clocked. While the magnitude of the power is not dramatically high, the relatively small area of the silicon die (the part of the processor containing the millions of transistors) makes the heat concentration (aka, heat flux) extremely high -- approximately 1 Megawatt per square meter.  This high concentration of heat is on par with a space shuttle re-entering earth’s atmosphere at 20,000 miles per hour, or the same intensity we’d feel from the sun if earth orbited 97% closer to it.  The maximum CPU die temperature varies but must always be maintained somewhat below the boiling temperature of water, ~100°C, so as not to damage the CPU.