Phoenix, Arizona – Residents across the Valley will face unhealthy air on Thursday as a High Pollution Advisory for ozone goes into effect in Phoenix on Aug. 21, 2025. State officials warn that prolonged outdoor exposure could pose health risks, especially for children, seniors, and those with respiratory issues.
According to the Arizona Department of Environmental Quality, the advisory covers Maricopa County and is expected to remain in place through Thursday evening. Ozone pollution tends to build up during the hottest part of the day, with concentrations peaking between 2 p.m. and 6 p.m.
The advisory means air quality may reach “unhealthy for sensitive groups” on the Air Quality Index. Health experts recommend limiting strenuous outdoor activity, carpooling or using public transit to reduce emissions, and keeping windows closed during peak afternoon hours.
City officials in Phoenix and surrounding communities, including Tempe, Mesa, and Glendale, are reminding residents to refuel vehicles after dark, avoid wood-burning fires, and postpone gas-powered yard work until evening.
The advisory expires at midnight, but ADEQ said additional alerts are possible if high ozone conditions persist into the weekend.
