The smoke from Canadian wildfires that seeped into Minnesota caused some of the poorest air quality ever in the state. Air quality monitors in Minnesota recorded the highest particulate readings on record Thursday.

Air quality is measured with the Air Quality Index or AQI. The AQI works sort of like a thermometer that runs from 0 to 500 degrees. Instead of showing changes in the temperature, the AQI is a way of showing changes in the amount of pollution in the air.

St. Cloud actually ended up having the worst air quality of anywhere else in the state with the air quality monitor recording 422 micrograms per cubic meter at 11 a.m. Thursday. That reading broke the record set a couple of hours earlier at Brainerd of 401 micrograms per cubic meter. The last record set was 397 micrograms per cubic meter set last week in Red Lake.

The smoke in the air was so bad it was even visible from space:

As of Friday morning at 5 AM the air quality still wasn't back to normal, as it was still at about 192 micrograms per cubic meter, falling in the "unhealthy" range. For reference, "Good" air quality is usually 0-50, "Moderate" is 51-100, "Unhealthy for sensitive groups" is 101-150, and "Unhealthy" is 151-200. Anything over 200 is considered very unhealthy.

There is an air quality alert in affect through Friday, July 30th at 3 pm, and areas of smoke and haze are predicted to hang around the area through the weekend.

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