From the Shanghai Daily:
Shanghai’s Central Meteorological Observatory issued a red fog warning at 4:25am today as the visibility dropped below 50 meters.
The observatory also reported the blinding fog in some parts of the city at 7:30am. The heavy fog is expected to last till noon.
We did a little (very little) searching and couldn’t find any meteorological occurrence commonly known as “red fog” so we are assuming it is just a color-coded warning level system akin to the Homeland Security Advisory System. But it seems to be a Shanghai-only thing, or at least a thing that is not commonly written about in English. There were only seven Google search results for the phrase “red fog warning” and three for “red fog alert” (one of which was another Shanghai Daily story that mentioned weathermen being forced “to sound a red fog alert” — does it really make a noise?).
And of course we all know about the Red Fog Alert, the four-year-old retired greyhound racing dog.
Image of DJ Red Alert from kooldjredalert.com.