Wildfires in Canada are sending heavy smoke across the northern U.S., and New Jersey is experiencing some unhealthy air pollution. The air quality has some Northeasterners wondering, what is the AQI, or Air Quality Index? AQI, or Air Quality Index, is the measure of how healthy or unhealthy the air is.

Smoke from Canadian wildfires is causing air quality concerns for millions of Americans in the Midwest and Northeast.  Air quality alerts were in effect Tuesday in several states, including Michigan and New York.

MINNEAPOLIS (FOX 9) - An air quality alert has been issued for all of Minnesota starting Sunday due to wildfire smoke from Canada. The Minnesota Pollution Control Agency (MPCA) has issued an air quality alert for all of Minnesota starting Sunday at 9 a.m. until 9 a.m. Tuesday.