Air quality comparison · United States, 939.5 mi (1512 km) apart
Chicago vs Houston Air quality index (AQI) today
Houston has cleaner air than Chicago right now: AQI 62 (Moderate) against 114 (Unhealthy for sensitive groups).
That puts them in different EPA bands, so the health advice differs today. But over the past 7 days, on modeled daily averages, Chicago averaged AQI 34 against 76, and it was the cleaner of the two on 7 of those days. Houston has lost more forest since 2001. Houston has more tree cover.
United States
AQI 114
Unhealthy for sensitive groups
Cleaner right now
- PM2.5
- 40.6 µg/m³2.7× WHO guideline
- Main pollutant
- PM2.5
- Source
- Ground station
- Reading
- Nov 11, 09:00 local
United States
AQI 62
Moderate
Cleaner right now
- PM2.5
- 15.1 µg/m³1.0× WHO guideline
- Main pollutant
- PM2.5
- Source
- Ground station
- Reading
- Nov 11, 09:00 local
Updated . Lower is better on the US EPA index: 0–50 is Good, above 300 is Hazardous. Measured by Airleaf.
Chicago114Houston62
Head to head
Chicago vs Houston at a glance
Houston is ahead on 4 of 6 measures, and Chicago on 2. The better figure in each row is marked.
| Chicago | Houston | |
|---|---|---|
| Air quality nowUS AQI. Lower is better. | 114 | 62 (better) |
| PM2.5Fine particles, µg/m³. | 40.6 | 15.1 (better) |
| Past week's averageUS AQI, 7 days. | 34 (better) | 76 |
| Forest lost since 2001Within 10 km of the center. | 5 acres (2 ha) (better) | 566 acres (229 ha) |
| Tree coverWithin 1.2 mi (2 km) of the center. | 8.2% | 15.6% (better) |
| Trees still neededTo reach a healthy canopy. | 82.9K | 44.9K (better) |
Air quality today
What is the air like in Chicago and Houston right now?
Houston has cleaner air than Chicago right now: AQI 62 (Moderate) against 114 (Unhealthy for sensitive groups). PM2.5 is setting the index in both.
Chicago's PM2.5 is about 2.7× the WHO's 24-hour guideline of 15 µg/m³. Houston's PM2.5 is about 1.0× the WHO's 24-hour guideline of 15 µg/m³.
Both readings come from nearby ground stations.
ChicagoHouston
Concentrations at the same moment as the index above, for the pollutants both places report. Lower is better. The dark marks on the PM2.5 and PM10 rows show the WHO's 24-hour guidelines (15 and 45 µg/m³).
The past week
Which had cleaner air over the past 7 days?
But over the past 7 days, on modeled daily averages, Chicago averaged AQI 34 against 76, and it was the cleaner of the two on 7 of those days. A single reading can catch a city on a bad afternoon; the week says whether it was the weather or the place.
- Cleaner days
- Chicago7Houston0
- Average AQI
- Chicago34Houston76
- Worst day, AQI
- Chicago52Houston97
The daily numbers (7 days)
| Day | Chicago | Houston |
|---|---|---|
| Nov 4 | 27 | 62 |
| Nov 5 | 32 | 97 |
| Nov 6 | 11 | 95 |
| Nov 7 | 32 | 77 |
| Nov 8 | 35 | 52 |
| Nov 9 | 47 | 69 |
| Nov 10 | 52 | 79 |
Daily averages from the CAMS atmospheric model for both places, so the week compares like with like. They can differ from today's reading at the top of the page wherever that comes from a ground station.
What it means today
Is it safe to go outside in Chicago and Houston today?
Chicago (AQI 114, Unhealthy for sensitive groups): Sensitive groups should limit long or intense outdoor activity.
Houston (AQI 62, Moderate): Unusually sensitive people should consider limiting long outdoor exertion.
Exercise outdoors
- Chicago
- Children, older adults and people with asthma or heart disease should cut down long or hard exercise.
- Houston
- Fine for most people; unusually sensitive people should take long or hard exercise easier.
Windows
- Chicago
- Close them to keep the outside air out.
- Houston
- Fine to open; close them if you are sensitive to pollution.
Masks
- Chicago
- Sensitive groups: an N95 outdoors.
- Houston
- Not needed for most people.
Air purifier
- Chicago
- Run one, especially in bedrooms.
- Houston
- Worth running if you are sensitive.
Against everywhere else
How do Chicago and Houston compare with the rest of the world?
Right now Chicago's air is cleaner than 17% of the 5,420 places Airleaf tracks, and Houston's is cleaner than 46%. Within United States, that is 2% and 20% of its 308 measured places.
Cleaner air than…
- Chicago
- Beats 17%
- Houston
- Beats 46%
More tree cover than…
- Chicago
- Beats 17%
- Houston
- Beats 36%
Includes model estimates as well as station readings, so it can differ from our most polluted and cleanest air rankings, which use station readings only.
Deforestation · 2001–2025
Which has lost more forest, Chicago or Houston?
Houston has lost more: about 566 acres (229 ha) of forest within 10 km of its center from 2001 to 2025, against 5 acres (2 ha) around Chicago. 540 acres (219 ha) of that was cleared for good, for farms, mines or towns.
Measured within 10 km of each center, from the yearly satellite maps of forest loss: a wider circle than the one for tree cover, because forest is usually lost at a city's edges.
Worst year: 2003, with under 1 ha lost.
Worst year: 2011, with 180 acres (73 ha) lost.
| Chicago | Houston | |
|---|---|---|
| Forest lost since 2001Cleared, burned or logged. | 5 acres (2 ha) (better) | 566 acres (229 ha) |
| Share of its forestOf what it had in 2000. | under 1% (better) | 11% |
| Cleared for goodTurned into farms, mines or towns. | under 1 ha (better) | 540 acres (219 ha) |
| Recent trend2021–2025 against the five years before. | Too little to call | Too little to call |
| Main known cause | Towns and roads (42%) | Towns and roads (95%) |
Satellite timelapses
Watch both change, year by year
A clear satellite photo a year of the land around each city. Press play, turn on the forest cleared since the first year, or drag the before and after.
Chicago
2018: satellite photo from August 2018 of a 5 × 5 km area in the city center.
Houston
2018: satellite photo from November 2018 of a 5 × 5 km area in the city center.
Trees
Which has more trees, Chicago or Houston?
Houston has more tree cover: 15.6% of the land within 1.2 mi (2 km) of its center against 8.2% around Chicago, or about 48,666 trees against 25,375.
The dark mark is each place's canopy target: 30% of the land, raised where air quality is poor.
| Chicago | Houston | |
|---|---|---|
| Trees standingEstimated from the canopy area. | 25.4K | 48.7K (better) |
| Trees still neededTo reach the target. Fewer is better. | 82.9K | 44.9K (better) |
| CO₂ absorbed each yearBy the trees already standing. | 558K kg | 1.1M kg (better) |
Tree cover on the satellite image
The same 1.2 mi (2 km) radius around each center, with the tree cover the satellite found marked on it.
Reading these numbers
How this comparison is made
Air quality index
The US EPA index, computed from current pollutant concentrations: ground stations where a place has them nearby, and the CAMS atmospheric model everywhere else. It moves hour to hour, so it is a snapshot rather than a verdict on either place. The guideline marks are from the WHO's 2021 air quality guidelines.
Trees and forest
Tree cover is the share of ground under canopy within 1.2 mi (2 km) of each center, read from Sentinel-2 satellite imagery at 10 m detail. It measures that circle, not the whole municipality, which is what makes the two comparable. Forest loss comes from the University of Maryland's Global Forest Change maps.
More on the method on the About Airleaf page.
Frequently asked
Chicago vs Houston: your questions answered
Is Houston cleaner than Chicago?
On air quality, yes, right now: Houston reads AQI 62 against 114, a gap of 52 points on the US EPA index. This is a live reading rather than an annual average, so it can reverse within a day. But over the past 7 days, on modeled daily averages, Chicago averaged AQI 34 against 76, and it was the cleaner of the two on 7 of those days.
Is it safe to exercise outdoors in Chicago and Houston today?
In Chicago, at AQI 114: Sensitive groups should limit long or intense outdoor activity. In Houston, at AQI 62: Unusually sensitive people should consider limiting long outdoor exertion.
Which has lost more forest, Chicago or Houston?
Houston has lost more: about 566 acres (229 ha) of forest within 10 km of its center from 2001 to 2025, against 5 acres (2 ha) around Chicago. 540 acres (219 ha) of that was cleared for good, for farms, mines or towns.
Which has more trees, Chicago or Houston?
Houston has more tree cover: 15.6% of the land within 1.2 mi (2 km) of its center against 8.2% around Chicago, or about 48,666 trees against 25,375. Both figures describe the same-sized circle of ground around each center, not the whole municipality.
How many more trees do Chicago and Houston need?
Chicago needs about 82,932 more to reach its canopy target of 35%, and Houston about 44,922 to reach 30%. The target starts at 30% of the land and rises where air quality is poor.
Are Chicago and Houston measured the same way?
The method is the same: the US EPA index for air, and Sentinel-2 satellite imagery at 10 m detail over an identical radius for trees. Both readings come from nearby ground stations. Nothing is adjusted for population, city limits or climate.
How often does the Chicago vs Houston comparison update?
The air readings refresh about once an hour, and each reading's local time is shown at the top of the page. Tree cover comes from the latest clear satellite image of each area (Sep 11, 2026 and Oct 19, 2026), and the forest figures are published yearly.
Keep going
Compare them with somewhere else
Build your own
Compare Chicago with somewhere else
This place
Chicago