Air quality comparison · Kenya, 442 km apart
Mombasa vs Nairobi Air quality index (AQI) today
Mombasa has cleaner air than Nairobi right now: AQI 43 (Good) against 111 (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, Nairobi averaged AQI 46 against 53, and it was the cleaner of the two on 7 of those days. Mombasa has lost more forest since 2001. Nairobi has more tree cover.
Updated . Lower is better on the US EPA index: 0–50 is Good, above 300 is Hazardous. Measured by Airleaf.
Mombasa43Nairobi111
Head to head
Mombasa vs Nairobi at a glance
Nairobi is ahead on 4 of 6 measures, and Mombasa on 2. The better figure in each row is marked.
| Mombasa | Nairobi | |
|---|---|---|
| Air quality nowUS AQI. Lower is better. | 43 (better) | 111 |
| PM2.5Fine particles, µg/m³. | 7.7 (better) | 39.5 |
| Past week's averageUS AQI, 7 days. | 53 | 46 (better) |
| Forest lost since 2001Within 10 km of the center. | 804 ha | 336 ha (better) |
| Tree coverWithin 2 km of the center. | 11.9% | 26.2% (better) |
| Trees still neededTo reach a healthy canopy. | 47.9K | 27.6K (better) |
Air quality today
What is the air like in Mombasa and Nairobi right now?
Mombasa has cleaner air than Nairobi right now: AQI 43 (Good) against 111 (Unhealthy for sensitive groups). PM2.5 is setting the index in both.
Nairobi's PM2.5 is about 2.6× the WHO's 24-hour guideline of 15 µg/m³.
Nairobi is read from a nearby ground station and Mombasa is a model estimate, so the two are not quite like for like.
MombasaNairobi
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).
Mombasa: Model estimate · no ground station nearby. Data: Open-Meteo / CAMS, US EPA index.
Nairobi: Ground station · Kitisuru, 9.2 km away. Data: OpenAQ · AirGradient.
The past week
Which had cleaner air over the past 7 days?
But over the past 7 days, on modeled daily averages, Nairobi averaged AQI 46 against 53, 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
- Mombasa0Nairobi7
- Average AQI
- Mombasa53Nairobi46
- Worst day, AQI
- Mombasa57Nairobi56
The daily numbers (7 days)
| Day | Mombasa | Nairobi |
|---|---|---|
| Nov 4 | 57 | 56 |
| Nov 5 | 47 | 41 |
| Nov 6 | 51 | 44 |
| Nov 7 | 53 | 52 |
| Nov 8 | 57 | 42 |
| Nov 9 | 53 | 44 |
| Nov 10 | 52 | 44 |
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 Mombasa and Nairobi today?
Mombasa (AQI 43, Good): Air quality is satisfactory for everyone.
Nairobi (AQI 111, Unhealthy for sensitive groups): Sensitive groups should limit long or intense outdoor activity.
Exercise outdoors
- Mombasa
- A good day to be active outside.
- Nairobi
- Children, older adults and people with asthma or heart disease should cut down long or hard exercise.
Windows
- Mombasa
- Open them to air the house.
- Nairobi
- Close them to keep the outside air out.
Masks
- Mombasa
- Not needed.
- Nairobi
- Sensitive groups: an N95 outdoors.
Air purifier
- Mombasa
- Not needed.
- Nairobi
- Run one, especially in bedrooms.
Against everywhere else
How do Mombasa and Nairobi compare with the rest of the world?
Right now Mombasa's air is cleaner than 67% of the 5,420 places Airleaf tracks, and Nairobi's is cleaner than 19%. Within Kenya, that is 80% and 0% of its 26 measured places.
Cleaner air than…
- Mombasa
- Beats 67%
- Nairobi
- Beats 19%
More tree cover than…
- Mombasa
- Beats 26%
- Nairobi
- Beats 60%
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, Mombasa or Nairobi?
Mombasa has lost more: about 804 ha of forest within 10 km of its center from 2001 to 2025, against 336 ha around Nairobi. 797 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: 2008, with 174 ha lost.
Worst year: 2001, with 103 ha lost.
| Mombasa | Nairobi | |
|---|---|---|
| Forest lost since 2001Cleared, burned or logged. | 804 ha | 336 ha (better) |
| Share of its forestOf what it had in 2000. | 28% | 9.2% (better) |
| Cleared for goodTurned into farms, mines or towns. | 797 ha | 307 ha (better) |
| Recent trend2021–2025 against the five years before. | Too little to call | Too little to call |
| Main known cause | Towns and roads (86%) | Towns and roads (79%) |
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.
Mombasa
2018: satellite photo from November 2018 of a 5 × 5 km area about 5 km southwest of the city center.
Nairobi
2017: satellite photo from January 2017 of a 5 × 5 km area about 5 km north of the city center.
Trees
Which has more trees, Mombasa or Nairobi?
Nairobi has more tree cover: 26.2% of the land within 2 km of its center against 11.9% around Mombasa, or about 82,310 trees against 31,478.
The dark mark is each place's canopy target: 30% of the land, raised where air quality is poor.
| Mombasa | Nairobi | |
|---|---|---|
| Trees standingEstimated from the canopy area. | 31.5K | 82.3K (better) |
| Trees still neededTo reach the target. Fewer is better. | 47.9K | 27.6K (better) |
| CO₂ absorbed each yearBy the trees already standing. | 693K kg | 1.8M kg (better) |
Tree cover on the satellite image
The same 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 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
Mombasa vs Nairobi: your questions answered
Is Mombasa cleaner than Nairobi?
On air quality, yes, right now: Mombasa reads AQI 43 against 111, a gap of 68 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, Nairobi averaged AQI 46 against 53, and it was the cleaner of the two on 7 of those days.
Is it safe to exercise outdoors in Mombasa and Nairobi today?
In Mombasa, at AQI 43: Air quality is satisfactory for everyone. In Nairobi, at AQI 111: Sensitive groups should limit long or intense outdoor activity.
Which has lost more forest, Mombasa or Nairobi?
Mombasa has lost more: about 804 ha of forest within 10 km of its center from 2001 to 2025, against 336 ha around Nairobi. 797 ha of that was cleared for good, for farms, mines or towns.
Which has more trees, Mombasa or Nairobi?
Nairobi has more tree cover: 26.2% of the land within 2 km of its center against 11.9% around Mombasa, or about 82,310 trees against 31,478. Both figures describe the same-sized circle of ground around each center, not the whole municipality.
How many more trees do Mombasa and Nairobi need?
Mombasa needs about 47,878 more to reach its canopy target of 30%, and Nairobi about 27,646 to reach 35%. The target starts at 30% of the land and rises where air quality is poor.
Are Mombasa and Nairobi 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. Nairobi is read from a nearby ground station and Mombasa is a model estimate, so the two are not quite like for like. Nothing is adjusted for population, city limits or climate.
How often does the Mombasa vs Nairobi 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 8, 2026 and Sep 4, 2026), and the forest figures are published yearly.
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