A dust-covered wheelchair is seen outside Sky Harbor International Airport during a dust storm in Phoenix, Arizona July 5, 2011. Visibility was reduced to zero in some areas as wind gust blew near 40 miles per hour, local media reported on Tuesday. (Xinhua/Reuters Photo)

A limousine driver wipes dust from his limo outside Sky Harbor International Airport during a dust storm in Phoenix, Arizona July 5, 2011. (Xinhua/Reuters Photo)

Motorists drive along Interstate-10 during a dust storm in Phoenix, Arizona July 5, 2011. Visibility was reduced to zero in some areas as wind gust blew near 40 miles per hour, local media reported on Tuesday. (Xinhua/Reuters Photo)

Motorists drive along 16th Street during a dust storm in Phoenix, Arizona July 5, 2011. Visibility was reduced to zero in some areas as wind gust blew near 40 miles per hour, local media reported on Tuesday. (Xinhua/Reuters Photo)

Customers sit outside a Starbucks Coffee cafe during a dust storm in Phoenix, Arizona July 5, 2011.(Xinhua/Reuters Photo)

Jason Wallace (R) wears a face mask as he sits with Emily Wallace inside Sky Harbor International Airport during a dust storm in Phoenix, Arizona July 5, 2011. The Wallaces' flight to Tucson was delayed due to the storm.Visibility was reduced to zero in some areas as wind gust blew near 40 miles per hour, local media reported on Tuesday. (Xinhua/Reuters Photo)

 

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