State-run TV warned of poor air quality and advised the elderly, those sick and children to take precautions. Banks and the Tehran Stock Exchange would remain open, the report said.

This is the second time that Tehran shuttered schools and government offices and the fourth bad sandstorm since mid-April. Schools and government offices in Tehran were closed for the first time on account of a sandstorm in May. However, the country’s west, along the border with Iraq, has seen frequent closures of schools and offices due to sandstorms.

Tehran is among the most polluted cities in the world. Experts blame poor government policies, desertification and low water levels, as well as climate change, for the frequency and intensity of recent sandstorms.