PHOENIX - A giant wall of dust, the second this month, rolled through the Phoenix area on Monday, turning the sky brown, creating dangerous driving conditions and delaying some airline flights.

The storm, also known as a haboob in Arabic and around Arizona, formed in Pinal County and headed northeast, reaching Phoenix at about 5:30 p.m.

The dust wall was about 3,000 feet high and was carried by winds of 25 to 30 mph, with gusts of up to 40 mph, said Austin Jamison, a meteorologist with the National Weather Service. Visibility was down to less than a quarter-mile in some areas, he said.

"You have suddenly very poor visibilities that come on with all the dense dust in the air," he said. "With poor visibilities, that makes for dangerous driving conditions, and that's arguably the biggest impact."

Some departing flights at Phoenix Sky Harbor International Airport were delayed because of the storm, said airport spokeswoman Julie Rodriguez.

Incoming flights from nearby cities including Los Angeles were being held until the storm cleared, she said. She did not know how many flights were delayed or whether any were canceled.

Another giant dust storm in Arizona caught worldwide attention on July 5. That storm brought a mile-high wall of dust that halted airline flights, knocked out power for hundreds of people and turned swimming pools into mud pits.

Jamison said Monday's storm was not as powerful or as large as the last one, and didn't last as long.

"It's kind of like a ripple in a pond where it spreads out, slows down and fades out," he said.

Rodriguez said visibility at the airport was better Monday than it was during the July 5 storm, which grounded flights for 45 minutes.

"It's not as bad as it was," she said. "It's reduced but it's not terrible."