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Air Quality Alert: What to know before heading outside in Chicago on Tuesday

By and Dominic Cannonito
Published  July 14, 2025 4:58pm CDT
Chicago
FOX 32 Chicago

The Brief

    • An Air Pollution Action Day is in effect Tuesday for much of the Chicago area, with AQI levels at 137 — unhealthy for sensitive groups.
    • Health officials urge at-risk groups to limit outdoor activity; only N95 or N100 masks offer protection from wildfire smoke.
    • Smoke from Canadian wildfires and a high-pressure system are driving poor air quality, but conditions should improve by midweek.

CHICAGO - The Illinois Environmental Protection Agency has issued an Air Pollution Action Day for Tuesday, July 15. 

These days are typically enacted when the air quality value is equal to or greater than a value of 101, which correlates to the color orange, for two or more consecutive days.

Measuring AQI values.

What we know:

An Air Quality Alert is in effect through midnight Tuesday night for the following counties: McHenry, Lake (IL), Kane, DuPage, Cook, Kendall, Grundy, Will, Lake (IN), Porter, LaPorte, Newton and Jasper.

As of mid-afternoon on Monday, July 14th, the air quality index value is at 137, which yields a warning about unhealthy air quality conditions for sensitive groups. 

The Illinois Department of Public Health, or IDPH, recognizes children, adults above the age of 60, and those with underlying respiratory or cardiovascular conditions as the most at risk for Air Pollution Action Days. 

Pictured is a map of the air quality in the Chicago area on Monday, July 14.

What you can do:

The IDPH recommends limiting outdoor exposure and avoiding strenuous activity if possible. N95 or N100 respirators, when worn properly, can offer protection to at-risk groups if outdoor activity cannot be avoided. Cloth or surgical masks do not protect your lungs from the wildfire smoke, but why?

Wildfire smoke particles are generally less than or equal to 2.5 micrometers. To visualize this, imagine splitting the width of a singular hair follicle 30 times.

Dig deeper:

So where is all the smoke and haze coming from? According to the Saskatchewan and Manitoba Public Safety Agencies, there are 177 active wildfires across both Canadian Provinces. The weather does the rest of the work.

On Sunday, July 13, an upper-level low pressure system blanketed much of the Great Lakes region in clouds, and as this system moved out of the area toward the northeast, high surface pressure built in behind it. High pressure in the Northern Hemisphere is characterized by a clockwise circulation, as seen below.

High pressure in the Northern Hemisphere is characterized by a clockwise circulation.

High pressure is characterized by sinking air. This typically results in sunny conditions, but it can also mean that particles in the upper atmosphere are pushed down toward the surface. 

What's next:

Conditions should improve midweek thanks to our next weather maker. 

The wind direction will shift Wednesday and especially into Thursday, so the haze and poor air quality should clear out for the latter half of the week! 

ChicagoWeatherNews