The Chinese capital, Beijing, has been hit by its eighth - and worst - sandstorm of the year.
People across Beijing are clearing up sand left by the storm
Millions of residents woke to find their city covered in a thin film of yellow dust after the storm blew in from the border of China and Mongolia.
Some are wearing face masks and hospitals reported increased numbers of patients with breathing problems.
Such storms occur annually, but experts say desertification in western China is increasing their frequency in the east.
Scientists blame poor farming practices and drought for the expanding desert, which now covers a third of the vast country.
The authorities in Beijing have planted trees around the capital to try to stem the spread of the desert.
'Restless and annoyed'
Across the city on Monday, residents were hosing down their homes, cars and monuments.
Parents have been told to keep their children indoors.
One taxi driver said the storms had brought him more business than usual, "because people don't want to stand on the road and wait for buses".
But for many others, such storms are nothing more than an irritant.
"I always feel like something is in my throat and it's very dry. My eyes get tired easily and I can't see things clearly," one woman told the BBC.
"The weather plays a big role in people's mood. On a day like this, I feel restless and annoyed. I am in a bad mood no matter what I do."