— forecast mean PM2.5 over next 24h · — actual next-24h mean · — persistence baseline (PM2.5 now) · red ticks: alert issued (P(max>150 µg/m³ in next 24h) ≥ threshold) · orange dots: actual exceedance
Hover a time for the forecast
Alert sensitivity (what-if threshold)
Regression — next-24h mean PM2.5 (test)
Alert — any hour >150 µg/m³ in next 24h (test)
Data: Beijing Multi-Site Air Quality (Chen, 2017), UCI ML Repository, CC BY 4.0. Model: scikit-learn HistGradientBoosting on causal features (lags, rolling stats, current weather, 24h weather trends). Uses only information available at forecast time; no weather forecasts are used, which a production system would add. Not a medical or official advisory tool.