About this tool
This page shows the latest reading from the one monitoring location that the azwebdata service holds under the city name "Siem Reap" — a single point anchored at about 13.37°N, 103.84°E in the town itself, not inside the Angkor archaeological park, which lies several kilometres north. Like every city page here, it is a station reading, not a town-wide average: the temple zone, the airport road and the hotel strip all sit beyond the point that produces the number. Siem Reap's air is shaped by a tourism economy on top of the seasonal pattern. Tour traffic — tuk-tuks, tour vans, shuttle buses, the generators that cover peak-season power demand — runs through the town every day, and in 2023 the provincial administration issued air-pollution guidelines after Ministry of Environment stations showed fine-particle levels exceeding standards, naming vehicle exhaust, grassland and forest fires, waste burning and construction among the sources. Dry-season burning on the surrounding plain adds regional haze on top of the town's own emissions, which is why a quiet town day can still show a moderate or worse card.
How it works
When you open the page, your browser asks the InKhmer API for the province id siem-reap. The service finds the station-table entry for that id — latitude 13.3671, longitude 103.8448, the town-centre anchor — and requests the latest air-quality snapshot azwebdata stores under the location name "Siem Reap". Azwebdata refreshes its scheduled Cambodian locations every thirty minutes and holds on-demand answers in a fifteen-minute cache, so the value you see is normally under half an hour old. If OpenAQ has no station for the location, OpenWeatherMap's modelled values are used instead, mapped onto the same AQI bands. The AQI number is derived from the PM2.5 concentration through the US EPA breakpoint table, falling back to PM10 when PM2.5 is missing. The single point behind it sits in town, so the card reflects the town-centre reading rather than the temple park: tree cover and distance from the traffic corridors mean the park can read differently, while smoke and haze during burning season blanket both. If the provider stops answering, the last good cached value is served; with nothing available, the page says "No air quality data at the moment".
Use cases
- A visitor checking the card the evening before an Angkor sunrise trip to decide whether the pre-dawn haze is likely to soften the view.
- A tuk-tuk driver planning a ten-hour shift, using the band to decide when a mask on the town routes is worth wearing.
- A guesthouse host advising guests who jog or cycle in the morning whether to train on the town roads or stay on the hotel grounds.
- A parent of a child with asthma checking the reading before school-run traffic picks up on the way to a town school.
- A cycling-tour organiser deciding in dry season whether a temple-loop ride should become a half-day trip.
- A traveller comparing this page with the Cambodia overview before choosing between temple days and town days.
Frequently asked questions
Does this reading cover the air at Angkor Wat and the temple park?
No. The number comes from the single monitoring location azwebdata holds under "Siem Reap", anchored in the town at about 13.37°N, 103.84°E — the archaeological park is several kilometres north and is not directly measured here. The park has more tree cover and sits away from the town’s traffic corridors, so it can read differently on a calm day; during dry-season burning, regional haze can blanket town and temples alike. Treat the card as the town reference, not the park’s reading.
Is this the official government reading for Siem Reap province?
No. The Ministry of Environment runs its own monitoring stations and publishes through its own channels — its data was what prompted the provincial air-pollution guidelines in 2023. This page is independent: it serves OpenAQ monitoring data, with OpenWeatherMap as fallback, collected through azwebdata for one location in the town. Use it as a convenient public reading, not a government bulletin.
Why is the air often worst from January to March?
That is the heart of the dry season, when dust and burning haze build up. Ministry of Environment monitoring has shown fine-particle levels exceeding standards in the province, and the 2023 provincial guidelines explicitly list vehicle exhaust, forest and grassland fires, waste incineration, landfill fires and construction as the sources pushing PM2.5 and PM10 up. Less rain means less washout, so the haze accumulates instead of being cleared by storms.
How much does tourism traffic matter for the town’s air?
It is the town’s everyday baseline. Unlike the rice belt, where seasonal burning dominates, Siem Reap town has a constant load of tuk-tuks, tour vans and shuttle buses, plus generator use during peak-season power strain. The 2023 provincial guidelines treat vehicle emissions as a primary driver of the measured exceedances. That means the card can sit moderate even outside burning season, on days when the town is simply busy.
How fresh is the reading on this page?
Azwebdata refreshes its scheduled Cambodian snapshots every thirty minutes and serves other locations through a fifteen-minute on-demand cache, so the freshest value is normally under half an hour old. Your browser requests the latest value when the page loads, and the card shows the time the monitor actually observed the reading. It is a snapshot, not a minute-by-minute feed and not a forecast.
What does the page show when the station is offline?
It degrades quietly rather than breaking. If the provider stops answering, azwebdata serves the last good cached value for the location, and the "Updated" line shows when that data was served. If nothing is available at all, the page shows "No air quality data at the moment" instead of an error or a made-up number.
Which pollutant drives the AQI for Siem Reap?
PM2.5 — fine particles small enough to reach deep into the lungs — in almost every reading. The upstream publishes raw concentrations per pollutant, and this service derives the headline AQI from the PM2.5 value using the US EPA breakpoints, falling back to PM10 when no PM2.5 sensor reported. The pollutant table on the card still lists PM2.5, PM10, ozone, NO₂, SO₂ and CO individually.
I am planning an Angkor sunrise visit — when should I check the card?
Check the evening before and again before you leave in the dark. The card is the town-centre reading, not the temple-park reading, but in dry season the haze layer that builds overnight blankets both — which is exactly the window of a sunrise trip, when the air has had all night to collect smoke and dust. A card in the moderate or worse bands in the evening is a reasonable hint that the sunrise will be hazy; the park itself, with its trees and distance from town roads, can still be a little better or worse than what the card shows.
Data and accuracy
Readings come through azwebdata, which holds one monitoring location under the city name "Siem Reap" — anchored at 13.3671°N, 103.8448°E in the town — and answers it from OpenAQ, with OpenWeatherMap as fallback, on a thirty-minute schedule with a fifteen-minute on-demand cache. The card shows that one location's most recent stored value at its observation time: a town-centre reading, not a temple-park reading, not a province-wide average, and not a forecast. AQI follows the US EPA bands in the scale section. The statements about Siem Reap's sources and dry-season exceedances are drawn from the cited sources (the 2023 provincial guidelines coverage and the Siem Reap–Angkor monitoring study), not measured by this site.
Sources
- OpenAQ — open air-quality data platform — OpenAQ
- OpenWeatherMap — Air Pollution API — OpenWeatherMap
- Air Quality Index (AQI) Basics — the US EPA bands — US EPA — AirNow
- Siem Reap issues guidelines to prevent air pollution in province (Khmer Times) — Khmer Times
- Air pollution and its impact of tropical heavy rainwater and dew water chemistry in the Siem Reap–Angkor region (IFDA 2019) — Copernicus Meetings / Waseda University & APSARA Authority
Content last reviewed 19 October 2026