We had no days in the red zone (unhealthy air) and just four days that reached code orange (unhealthy air for sensitive groups, such as children, elderly people and people with respiratory illness.)
Cooler summer weather helped, but that doesn’t tell the whole story. There were 18 days when the temperature reached above 90 degrees in D.C., but the higher temperatures didn’t necessarily bring unhealthy air quality.
The Council of Governments credits reduced emissions from power plants, passenger vehicles, trucks and buses. Also, they say, more vehicles on the road are powered by electricity and natural gas.