Metro Phoenix's trend of hazy and cloudy skies continued on Thursday morning.
Matt Salerno, lead meteorologist with the National Weather Service in Phoenix, said the haze was the result of a dust storm that rolled through metro Phoenix about 1 a.m. on Thursday, Aug. 6.
He said there was a large storm system that moved through southern Arizona, pushing winds and dust toward the Valley. It caused gusts between 40-45 mph in the Phoenix area and dropped visibility to about 1 mile. As of Thursday morning, visibility was only about 4-5 miles.
Salerno said it's not unusual to see these back to back dust storms happen during Arizona's monsoon.
"They don't tend to happen every day, but they can happen every few days," he said. "As of recently the dust has
been pretty bad because we haven't had a ton of rainfall in the central parts of the valley to keep the dust down.
Salerno added that the southern winds are always a big source of dust storms in metro Phoenix.
"Our source region is mainly from Pinal and Pima counties and all the dust gets shoved up into Maricopa County," he said.
However, winds were expected to come from the north and northeast on Thursday night and Friday morning, indicating another dust storm was unlikely.
Why is the air quality bad today?
The poor air quality that has plagued metro Phoenix this week was due to the dust that was still in the air from previous storms on Monday and Wednesday nights.
The ASU School of Geographical Sciences and Urban Planning noted that the dust storm that hit on Aug. 3-4 lasted 15 hours and created the second highest concentrations of dust ever recorded. This made the storm a Category 5 on the Phoenix Dust Storm Scale; it was the fifth storm in 16 years to reach that highest category.
As a result of the storms, the air quality was 125 in Phoenix, which is considered "unhealthy" and can cause issues for sensitive groups with health problems, according toAccuWeather. The air quality was expected to remain in the unhealthy range through Friday.
Air quality is measured on a scale of zero to 500, with zero to 50 being good, 51 to 100 being moderate, 101 to 150 being unhealthy for sensitive groups, 151 to 200 being unhealthy, 201 to 300 being very unhealthy and 301 to 500 being hazardous and a health emergency.
Will it rain in metro Phoenix?
While most metro Phoenix residents associate a big dust storm with rain, Salerno said storms were unlikely in the Valley for the coming days. Rain chances remained at less than 10% through Saturday, though they were expected to increase to 20-30% by Sunday and through early next week.
"Maybe early next week we'll finally break that stagnant pattern we've been under," Salerno said.
He attributed the lack of storms to a strong high pressure system that has been stationed above the Valley, thus surpressing storm chances.
However, the haze and morning cloud cover has kept temperatures down in the 105-110 degree range, rather than hovering around 115 degrees, he said. Highs were expected to hit 108 degrees on Thursday before gradually creeping upward over the next few days, peaking at an expected 112 degrees on Saturday.
Salerno also warned that the humidity was expected to remain high, creating a muggy feeling in the air.
This article originally appeared on Arizona Republic: Why is air quality so bad in Phoenix? What to know about ongoing haze
