Minnesota's air quality is about to get a lot worse.

The Minnesota Pollution Control Agency has extended an air quality alert that was to end Friday afternoon until 3 p.m. Tuesday for the entire state. The worst of it will arrive on Saturday morning, with a "very unhealthy" air forecast for the Twin Cities metro area stretching in a broad area north to the Canadian border. The rest of the state is also under alerts of "unhealthy" or "unhealthy for sensitive groups."

The agency warned people with health sensitivities to stay indoors and everyone else to avoid prolonged exertion outside.

Even before the extended alert, the smoke coming from fires burning in Canada had already led to the worst air quality Minnesota has ever had on record.

Alex Chhith • 612-673-4759