What it means
Air quality adds context about pollution or smoke that can affect health and outdoor time.
How we calculate it
We compare air quality readings and public pollution records. Cleaner, more consistent air improves the climate signal.
Sources and freshness
AQICN, EPA, OpenAQ, and public air quality records.
Source periods vary by place. City pages show dated source context for the applicable measure when it is available.
Limitations
Monitor coverage varies, and short smoke or pollution events can differ from longer term conditions and neighborhood level exposure.