Smoke from Canadian fires is pouring into the US and could linger for days

Smoke from wildfires in Canada is moving into parts of the central US and could linger in the days ahead, health and weather officials warned Thursday.

Air quality alerts have been posted as of early Friday across several states, including Nebraska, Washington, Montana and Wisconsin, with a special weather statement about air quality in Wyoming.

The heaviest smoke concentrations should shift further east into the Midwest later in the day, affecting major metro areas including Chicago, Indianapolis and St. Louis.

Canada has had an especially active start to the fire season. Last week, devastating wildfires in Alberta had burned more than 150 times more area in that province than in the last five years combined by the same point in the year, CNN has reported.

In Nebraska, "Canadian wildfire smoke is going to move through the area today through tomorrow morning, resulting in potentially dangerous air quality and poor visibility across eastern Nebraska and Iowa. Limit outdoor activities if possible when the air quality is poor!" the National Weather Service in Omaha tweeted Thursday.

Wildfire smoke "is beginning to move into the Lincoln and Omaha metro areas," the service's Omaha office said Thursday afternoon. "Visibility should drop to 1-2 miles within the next couple of hours and air quality will go into the unhealthy range for sensitive groups."

In eastern Nebraska's Douglas County - which includes Omaha - the health department warned smoke could remain through Saturday.

The US Environmental Protection Agency's Air Quality Index indicated parts of the Rockies, the Great Plains and the Midwest, including the Nebraska Panhandle and northeast corner of the state, had "very unhealthy" air quality early Friday.

CNN's Dave Hennen contributed to this report.