How this works

This is NOAA's HRRR near-surface smoke forecast — modeled fine-particulate (PM2.5) smoke concentration near ground level across the continental United States. Each model run produces a sequence of hourly forecast frames; press play to animate the loop, or drag the slider to scrub through the hours. The two white dots mark Charlevoix, Michigan, and Bruce Mines, Ontario.

Frames are fetched from NOAA only when a person views them, then cached and shared with everyone else, so the loop loads quickly and NOAA is queried sparingly. Because near-surface smoke is essentially PM2.5, it maps onto the EPA Air Quality Index: the "rescale and recolor for AQI" toggle repaints NOAA's many smoke shades into the six EPA AQI categories using the 2024-revised PM2.5 breakpoints. This is approximate — the official AQI uses a 24-hour average of total PM2.5, while HRRR reports hourly, smoke-only values.