mist

Soccer goal posts are seen in the autumn mist at Dukes Meadows in Chiswick, west London...Soccer goal posts are seen in the autumn mist at Dukes Meadows in Chiswick, west London November 13, 2013. REUTERS/Toby Melville

Toby Melville/Reuters

Goalposts in the autumn mist at Dukes Meadows in Chiswick, west London, early on Wednesday morning. Read more

A traffic policeman signals to drivers during a smoggy day in Harbin, Heilongjiang province, October 21, 2013. The second day of heavy smog with a PM 2.5 index has forced the closure of schools and highways, exceeding 500 micrograms per cubic meter on Monday morning in downtown Harbin, according to Xinhua News Agency.

China Daily/Reuters

A traffic policeman signals to drivers during a smoggy day in Harbin, Heilongjiang Province. The second day of heavy smog forced the closure of schools and highways on Monday, according to Xinhua News Agency.

Sunrise Over The Somerset Levels...SOMERSET, UNITED KINGDOM - SEPTEMBER 04:  The dawn sun begins to clear the mist and fog lingering in fields close to the city of Wells on September 4, 2013 in Somerset, England. Parts of the UK are set to enjoy a late summer heatwave today, with temperatures possibly reaching 28C in central, eastern and southern England, with temperatures predicted to climb even higher tomorrow.  (Photo by Matt Cardy/Getty Images)

Matt Cardy/Getty

The sun begins to clear the mist and fog lingering over fields close to the city of Wells in Somerset, England.