Smoke from Canadian wildfires descended on the Chicago area, making for hazy skies and bringing a burnt odor across the region as air quality alerts sparked warnings for many to stay inside.
The smoke made for dangerous conditions, with levels reaching a "very unhealthy" status and inching closer to the "hazardous" threshold.
Beaches were shut down in some locations, summer camps canceled and events moved indoors as experts and officials urged people to wear masks when possible.
Video from cameras around the city showed the clouds of smoke that appeared almost fog-like conditions around the city. Smoke made for limited sunshine and clouded the tops of downtown buildings, making for eerie scenes.
According to the government air quality website, AirNow, the PM2.5 -- an air pollutant also known as fine particulate matter, which is causing much of the haze in the region -- reached 258 as of 3 p.m., and stayed there through 5 p.m. By comparison, levels were at 209 at 11:30 a.m. and 228 at 1 p.m.
Anything over 200 is considered "very unhealthy, though in the last month, the city hasn't seen its numbers climb above 160. Once the region reaches above 300, it enters a "hazardous" level.
According to the World Air Quality Index, which ranks cities across the globe from worst air quality to best, Chicago currently holds the No. 1 spot -- and that was before levels rose even higher.
The National Weather Service also issued an air quality alert around that same time that remains in effect until midnight Wednesday, though conditions are expected to be "unhealthy for sensitive groups" across Illinois Wednesday.
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The NWS reported smoke from wildfires in Canada is moving into the region and "pushing air quality into the unhealthy or worse categories." The agency urged people to reduce or limit outdoor activities.
Chicago Department of Public Health Commissioner Dr. Allison Arwady said reaching such a level is "unusual" in the Chicago area.
"It's actually pretty unusual for us to fall into it based on that PM2.5," she said. "Our ozone is actually good right now, so it's the PM2.5 - it's at a higher level."
In total, there are six categories: green, or good; yellow, or moderate; orange, or unhealthy for sensitive groups; red, or unhealthy; purple, or very unhealthy; and maroon, or hazardous.
According to data from AirNow, Chicago hasn't climbed above 160 for PM2.5 at all within the last month. The region has only reached above 150, entering the "red" category, just three times since May 28.
