Well, I arrived in Harbin on October 18th and the weather was, let's say as a normal January in Hamburg and I was stupidly dressed with a linen jacket and mocassins - just out of Rome. January in Harbin could be worse. Wikipedia says - 13 C is the medium High Temperature, they call it also Ice -City in China.
Harbin is known for it's pollution problems and the picture below, taken from my Hotel room might confirm this.

But my normally quite sensitive nose was not so much hurt. The fact that Harbin municipality introduced years ago successfully a "cap and trade" approach before China had ratified the Kyoto Protocol, could be a reason.
Harbin is not as shiny as Beijing, Shanghai or Guangzhou, the airport is compared to the other 3 pieces of art a shabby building from the 80s. But also Harbin is a constructionside everywhere.
Worth to see the central street with a very "nordic" style.