Smoke from Canadian wildfires started making air quality worse in the eastern U.S. on Wednesday as several Midwestern states battled conditions deemed unhealthy by the federal government. The fires have forced thousands of Canadians to flee their homes and sent smoke as far as Europe. In the U.S., smoke lingered on the skylines of cities from Kansas City to Minneapolis, and a swath of the region had unhealthy air quality Wednesday, according to an Environmental Protection Agency map. Parts of Maine, Vermont, New Hampshire and New York had areas of moderate air quality concern, and officials advised sensitive people to consider reducing outdoor activity. The Minnesota Pollution Control Agency issued an alert for almost the entire state into Wednesday, but the Twin Cities area got the region's worst of it Tuesday. The U.S. Environmental Protection Agency's AirNow map showed a swath of red for “unhealthy” conditions across Wisconsin and northern Iowa. Conditions in northern Michigan also reflected many unhealthy zones. The Air Quality Index was around 160 in many parts of the upper Midwest, indicating poor conditions. The Air Quality Index — AQI — measures how clean or polluted the air is, indicating which health effects might be experienced within a few hours or days after breathing polluted air. It is based on ground-level ozone, particle pollution, carbon monoxide, sulfur dioxide and nitrogen dioxide. Particulates are the main issue from the fires. The index ranges from green, indicating satisfactory air quality that poses little or no risk, to maroon, which is considered hazardous. That level comes with health warnings of emergency conditions which are more likely to affect everyone. There were areas of reduced air quality all over the U.S. on Wednesday, with numerous advisories about moderate air quality concerns as far from the fires as Kansas and Georgia. Canada is having another bad wildfire season. Most of the smoke reaching the American Midwest has been coming from fires northwest of the provincial capital of Winnipeg in Manitoba. Canada’s worst-ever wildfire season was in 2023 and choked much of North America with dangerous smoke for months. This season's Canadian wildfires are so large and intense that the smoke is even reaching Europe, where it is causing hazy skies but isn’t expected to affect surface-air quality, according to the European climate service Copernicus. The smoke over western Europe is expected to keep moving eastward, according to the National Oceanographic and Atmospheric Administration. It’s causing hazy skies, but not expected to affect surface-air quality. However, it could rise high enough to be carried that far, indicating the immense size and intensity of the fires, according to Copernicus.