Early-season 2023 wildfires generated record-breaking surface ozone in the Upper Midwest

The GOES-18 satellite captured this image of Canadian wildfire smoke in May 2023. Credit: NOAA

During the summer of 2023, Canada experienced its most intense wildfire season on record. More than 40 million acres burned, an area the size of Georgia, injecting an enormous amount of smoke into the atmosphere, where photochemical reactions generated ozone pollution. In late spring, which is early for the wildfire season, wave after wave of smoke billowing from burning forests in western Canada poured across the sky and into the upper U.S. Midwest.

A new analysis by NOAA’s Chemical Sciences Laboratory (CSL) found that ozone pollution readings in the Upper Midwest caused by these massive fires were the worst in decades.