Dallas, TX Air Quality Index (AQI) Today

On the days that matter, Dallas stands upwind of its own pollution. TCEQ’s conceptual modeling for the Dallas–Fort Worth nonattainment area describes hot, slow, southeasterly flow carrying the urban plume northwest across the region, with the ozone finishing its formation well downwind of where the ingredients were emitted. The measured result is that the region’s highest ozone design values sit at monitors on the northwest side, Keller and Grapevine and Eagle Mountain Lake among them, and the lowest sit east and southeast of the city, on the side the air reaches first.

That has a specific consequence for a reading taken in Dallas. It is often closer to a measure of what entered the metro than of what left it, and on a southeast-flow afternoon the same hour can be dirtier thirty miles up the road in Tarrant or Denton County than it is over downtown.

Particles keep their own calendar. From late June into mid-August, Saharan dust that has crossed the Atlantic and the Gulf can turn the sky milky and push readings into the moderate range with nothing local changing at all. Smoke from fires well outside Texas does the same whenever the pattern delivers it. Neither is a Dallas emission, and both are Dallas readings.