Minnesota faces worst air quality due to wildfire smoke and ozone.
An air-quality alert has been expanded as pollution levels have reached unhealthy levels for all groups in the New York City area. The alert, which was initially issued for sensitive groups, has now been extended to include everyone. The high levels of pollution are due to a combination of factors, including high temperatures, low wind speeds, and emissions from vehicles and power plants. People are advised to limit outdoor activities and to use public transportation instead of driving.