<p><strong>A flash of lightning accentuates a thick blanket of dust over Gilbert, <a href="http://travel.nationalgeographic.com/travel/united-states/arizona-guide/">Arizona</a>, on Thursday—the third major dust storm to hit the <a href="http://maps.nationalgeographic.com/map-machine#s=r&amp;c=33.436025510720334, -112.0269012451172&amp;z=10">Phoenix metropolitan area (map)</a> since early July. </strong></p><p>The billowing cloud of dust was about a half mile (0.8 kilometer) high and 50 to 55 miles (80 to 88 kilometers) wide. The storm rolled across Arizona's Pinal County last night with winds reaching 30 to 40 miles (48 to 64 kilometers) an hour, the <em>Arizona Republic</em> reported.</p><p>Dust storms are relatively common between June and September in parts of the U.S. Southwest. Severe dust storms are also called haboobs—Arabic for "violent wind"—since they often appear in northern Africa and the Middle East. (See a <a href="http://news.nationalgeographic.com/news/2005/04/0429_050429_iraqduststorm.html">picture of a haboob in western Iraq</a>.)</p>