Beijing residents awoke to heavy smog on Thursday, with “hazardous” Air Quality Index (AQI) readings across the capital.

The Beijing and national meteorological authorities issued a blue alert as a sandstorm hit the region – the highest level on the warning system.

Readings at the Temple of Heaven exceeded 905 on the AQI. The US embassy in Beijing gave a reading of 506 as of 10am Thursday.

In Langfang, readings were off the charts, exceeding 999 on the index.

Stations across northern China, in Heilongjiang, Liaoning and Inner Mongolia also gave “beyond index” readings.

Readings of over 300 are considered hazardous to health, with residents advised to avoid all outdoor exertion.

Fine dust and sand particles are often whipped up from the Gobi Desert during the spring months. The blue alert is expected to remain in place until Friday.

Residents took to social media, with Twitter users calling the toxic smog “depressing” and “crazy.”

Tom Grundy

Tom is the editor-in-chief and founder of Hong Kong Free Press. He has a BA in Communications and New Media from Leeds University and an MA in Journalism from the University of Hong Kong. He has contributed to the BBC, Euronews, Al-Jazeera and others.