Dangerous levels of smoke from the Canadian wildfires are once again battering the United States, spanning throughout the Midwest and hitting Chicago the hardest. The Windy City entered the purple zone on Tuesday with an air quality index of 228, which is considered “very unhealthy” and increases the risk of health impacts for everyone—but especially those belonging to sensitive groups, according to AirNow. Milwaukee also entered the zone with an index of 221, and multiple states such as Illinois, Wisconsin, Indiana, and Michigan are seeing “unhealthy” amounts of smoke blanketing their skies. The haze may also strike again in New York City, where the unbreathable smoke creeped into the “hazardous” zone earlier this month as the then-most polluted city on Earth. In a tweet, Mayor Eric Adams warned that air quality could worsen in the city on Wednesday and recommended residents prepare to wear a mask outdoors.