Historical AQI Data: How to Access Past Air Quality Records
Last updated: December 2024 · Complete guide to historical air quality data sources
Best Free Sources for Historical AQI Data
The most comprehensive free historical air quality database. Aggregates data from 10,000+ government monitoring stations across 100+ countries. Free API with hourly data back to 2013 for many stations. No registration required for basic access.
Official US EPA Air Quality System. Hourly and daily data going back decades. Every monitoring station in the US. Pre-computed AQI values and pollutant concentrations. Free download.
IQAir publishes annual World Air Quality Reports with city-level PM2.5 annual averages for 7,000+ cities. The report series goes back to 2018 and is widely cited. PDF download free.
India's Central Pollution Control Board. Official historical data for Indian cities. Also available through the CPCB Bulletin and SAMEER mobile app.
European Environment Agency. Historical PM2.5, PM10, NO2, O3 for all EU member states. Goes back to 2000+ for many stations. Downloadable datasets and interactive maps.
Worst Air Quality Days on Record — Major Cities
| City | Date | Peak AQI | Cause |
|---|---|---|---|
| Delhi | Nov 7, 2023 | 999 | Diwali + stubble burning combo. PM2.5 hit hazardous ceiling |
| Lahore | Dec 21, 2023 | 985 | Extreme winter inversion, brick kilns, zero wind for 5 days |
| New York | Jun 7, 2023 | 484 | Quebec wildfire smoke — worst air quality in NYC history |
| Chiang Mai | Mar 30, 2023 | 312 | Forest burning season peak, AQI exceeded 300 for 11 days |
| Kraków | Jan 15, 2017 | 450 | Pre-coal ban winter; city suspended all outdoor activities |
| Beijing | Jan 12, 2013 | 755 | The "Airpocalypse" — China's smog wakeup call. Triggered national action |
| Jakarta | Aug 17, 2023 | 276 | Peatland fire smoke transport + stagnant air over Indonesia |
| Milan | Feb 5, 2024 | 198 | Extended high-pressure inversion — 3-week smog event |
10-Year Annual PM2.5 Trends — Selected Cities
| City | 2013 | 2017 | 2020 | 2023 | Trend |
|---|---|---|---|---|---|
| Beijing(China) | 89 | 58 | 38 | 32 | ↓ Improving China's "Blue Sky" program cut PM2.5 64% in 10 years — largest documented improvement in history |
| Delhi(India) | 98 | 112 | 84 | 92 | → Flat Worst pandemic year saw improvement; post-pandemic rebound erased gains |
| Los Angeles(USA) | 14 | 13 | 11 | 16 | ↑ Worsening 2020 wildfires + 2023 wildfires pushed PM2.5 up; long-term improvement trend reversed |
| London(UK) | 15 | 12 | 9 | 9.8 | ↓ Improving ULEZ, diesel scrappage, wood stove restrictions driving sustained improvement |
| Lahore(Pakistan) | 120 | 135 | 128 | 148 | ↑ Worsening Continued deterioration — brick kilns, vehicle growth outpacing any control measures |
Units: μg/m³ annual average PM2.5. Sources: IQAir World Air Quality Reports 2013–2023, EEA, CPCB, EPA.
Seasonal Patterns in Historical Data
October–February worst (crop burning + winter inversion). Pre-monsoon April–May second peak. Monsoon June–September cleanest due to rain washout.
January–March worst (heating season + spring dust storms). July–August cleanest due to summer rainfall. October–November second peak as heating begins.
December–February worst (temperature inversions, heating). April–May and August best. Saharan dust events can spike PM10 regardless of season in southern Europe.
Wildfire smoke (July–October) now the dominant annual PM2.5 driver. Traditional winter smog season has diminished. Fire season episodes can be the worst air quality in a decade.
Frequently Asked Questions
Where can I download historical AQI data for free?
OpenAQ (openaq.org) is the best free source for global historical hourly data. For US cities, the EPA AQS Data Mart provides the most complete dataset. For European cities, the EEA data portal covers all EU member states back to 2000. For India, CPCB provides data through the SAMEER app and bulk downloads.
How far back does historical AQI data go?
It depends on the country and monitoring network. For US cities: EPA has continuous monitoring data back to the 1980s–90s. Europe: EEA data covers 2000+ for many stations. India: Continuous modern PM2.5 monitoring started around 2015. China: Reliable city-wide PM2.5 data from 2013 when the national network was deployed. Many developing countries have only 2–5 years of data.
What was the worst air quality ever recorded in a major city?
The highest documented AQI values in major cities: Delhi regularly hits 500–999 AQI (hazardous ceiling) during November smog events. Lahore exceeded 1,000+ in December 2023. Beijing's "Airpocalypse" on January 12, 2013 reached AQI 755. New York hit AQI 484 on June 7, 2023 due to Quebec wildfire smoke — the worst since monitoring began.
How has air quality changed over the past decade globally?
The global picture is mixed. China has dramatically improved — Beijing's annual PM2.5 dropped from ~89 μg/m³ in 2013 to ~32 μg/m³ in 2023, a 64% reduction. Europe shows slow but consistent improvement. The US has improved long-term but wildfire smoke is reversing gains in western states. South Asia (India, Pakistan, Bangladesh) has worsened overall, driven by economic growth outpacing regulation.
Can I get historical AQI data for a specific address or neighborhood?
Government monitoring networks provide data at the station level, not by address — stations are typically spaced 5–30 km apart. For neighborhood-level historical data, low-cost sensor networks like PurpleAir (purple.air.com) have data back to 2017 for US cities, though lower measurement quality. Hyperlocal historical data at the address level is generally not available.