Yesterday's Air Quality Maps

Peak AQI

Maps showing the peak Air Quality Index (AQI) are created by the Air Quality Mapping System from ozone and particle data gathered from a nationwide network of state and local air monitoring stations. The maps show the highest AQI for each area during the 24 hour midnight to midnight period from either 8-hour ozone or 24-hour particle pollution. Peak 8-hour ozone concentrations typically occur at different times at different monitors. Thus, the maps provide the viewer with an indication of the worst air quality during the course of the day.

Peak Ozone AQI

Peak ozone maps are based on the highest 8-hour ozone concentrations measured at each ozone monitoring station. Peak ozone concentrations typically occur at different times at different monitors. Thus, peak maps do not represent a "snapshot" of air quality at any one moment. Rather, they provide the viewer with an indication of how the air quality may have been at its worst in his or her area during the course of the day.

Color ozone maps are available during the ozone season, May 1 – September 30.

PM 2.5 AQI

Particle pollution maps are based on the midnight to midnight 24-hour average concentrations measured at each particle monitoring station. The maps show the 24-hour average particle concentrations in accordance with EPA’s Air Quality Index for particles and are available year round.