This measure, based on data from the Environmental Protection Agency, evaluates states on the number of days the Air Quality Index in counties was not rated “good.” U.S. News calculated a ...

It comprises two measures: the number of days with an air quality index below a certain threshold and the number of violation points against drinking water systems in each state. Learn more about ...

and forecast models to provide real-time air quality index (AQI) readings for more than 1,000 locations. Los Angeles’ air quality is closely tied to weather patterns. Clear, breezy days help ...