Ahvaz, Iran

Ahvaz is built on the banks of the Karun River and is situated in the middle of Iran’s Khūzestān Province. Although it has a population of roughly 1,425,891, it is considered a desert, with long, extremely hot summers that often bring sandstorms and dust storms. In 2011, the World Health Organization ranked Ahvaz as the world’s most air-polluted city.

Highest recorded temperature - 128.3 degrees F