The highest air temperature ever recorded on Earth was in the U.S.

Explanation

It was 56.7°C (134.1°F) recorded in 1913 at Furnace Creek Ranch in Death Valley, California. Other readings have exceeded it in some deserts, but those are ground surface readings and not air temperatures. The 1913 reading has been questioned by some meteorologists (it's suspiciously out of line with surrounding weather stations), but it stands as the official WMO record.