The wall of dust moved across the desert from the south on Tuesday and descended on the valley by nightfall. KSAZ-TV reported the storm appeared to be roughly 50 miles (80 kilometers) wide.
The National Weather Service says strong winds with gusts of more than 60 mph (100 kph) were moving northwest through Phoenix and the cities of Avondale, Tempe and Scottsdale. More than a dozen communities in the area also were under a severe thunderstorm watch until 11 p.m.
The Federal Aviation Administration said on its website that because of low visibility in the area, no Phoenix-bound flights were allowed to leave Las Vegas or Los Angeles airports until 9 p.m.