Ozone Levels Running High Across DFW Today

If you were planning a lunchtime run on the Flower Mound trail system or an afternoon of yard work, today's the day to rethink the timing.

The Texas Commission on Environmental Quality issued an Ozone Action Day for the Dallas-Fort Worth area today, Thursday, September 17. The National Weather Service Fort Worth office relayed the alert, which covers Denton County along with the rest of the metro. Light winds, warm temperatures, and enough afternoon sunshine are pushing ozone into the middle to upper end of the "Moderate" range across parts of DFW, with the highest concentrations expected in the afternoon and early evening.

Ozone doesn't arrive the way rain does. You won't see it or smell it. It forms at ground level through chemical reactions that sunlight triggers between nitrogen oxides and volatile organic compounds — the stuff coming out of vehicle tailpipes, industrial facilities, and gasoline vapors. The problem builds through the day and peaks when it's hottest and stillest outside. Right now, that's your afternoon commute window and after-school hours.

The TCEQ describes ground-level ozone as "a respiratory toxic agent that can cause acute respiratory health effects when people breathe high concentrations of it over several hours," including decreased lung function and aggravated asthma symptoms. People with asthma, emphysema, COPD, and heart disease are most at risk. Kids count too — their lungs are still developing, and they tend to be outside longer.

Today is also not an isolated bad day. North Central Texas is already in non-attainment for ozone, which means days like today are part of a pattern Denton County residents have lived with for years.

The practical adjustment is straightforward: shift anything strenuous — a run, flag football, mowing — to early morning or after sunset. The EPA recommends checking the Air Quality Index at AirNow.gov for a current air forecast and guidance on what to do with the numbers. If anyone in your household uses a rescue inhaler, keep it accessible today through the afternoon peak.

The alert covers one day only and has to be renewed each day it applies, so check back tomorrow morning if your schedule puts you outside again. You can sign up for TCEQ email or text alerts at tceq.texas.gov so future Ozone Action Days reach your phone before you lace up your shoes.