A dramatic dust storm has blanketed Arizona, grounding flights and blinding drivers.

Towering clouds of dust rolled through cities in the south west such as Phoenix, knocking out power and darkening the sky.

Extraordinary footage showed the storm obscuring skyscrapers as it moved across the ground at 45mph.

Two million people across Arizona were put on a dust storm watch with the National Weather Service warning of low visibility and strong winds.

The storm was so powerful that temperatures in Phoenix dropped from 100F (38C) to 75F (24C) as it passed, according to ABC News.