Millions of residents in the upper Midwest and Northeast are at risk due to poor air quality, which can exacerbate respiratory and cardiovascular conditions. Vulnerable groups, including children, older adults, and individuals with pre-existing health issues, are particularly affected. Cities like New York, Boston, and Philadelphia are experiencing significant smoke levels, while extreme heat further compounds health risks. Air quality alerts are in effect from Minnesota to New York City, with some areas reaching dangerous levels for all residents.