City air quality, in one paragraph

city-air-quality in one paragraph, for anyone deciding whether it is worth downloading.

5,480 rows, 8 columns, one row per city per day. Daily pollutant readings for four cities over nearly four years, with strong seasonality, weekday effects, wildfire episodes, and genuine sensor outages.

Every dataset here is synthetic, which is a deliberate trade. It costs realism and buys three things: we can ship it CC0 with no licence trap, we can bake in the exact quirk a lesson needs, and nobody's real records end up in a tutorial.

Something to try: Decompose PM2.5 into trend, seasonality, and remainder. The SQL playground has it loaded already, and the data explorer will profile every column in one pass if you would rather look before you query.

select *
from city_air_quality
limit 20;

The file is generated from a fixed seed, so the CSV you download today is byte-identical to the one from last year. That matters more than it sounds: it means a lesson can say "row 412 is the interesting one" and still be right in eighteen months.

Download it, break it, keep it. CC0 — no attribution required, no account, no email.