Directory
One page per city, each answering the same question: how bad is the air here, and when does it clear. Each level here is read when this page loads and carries the time it was read. Open a city for its clear time and the rest of the forecast. Every hour shown on any of these pages is a model estimate, not a measurement.
Every city page leads with one answer: the clear time. It is the first stretch of at least six straight hours where the forecast drops below the Hazy threshold and stays there. The six-hour hold is the whole point of the rule. Smoke does not leave cleanly. It thins for an hour, comes back, thins again, and a forecast that announced the first dip as the all-clear would be wrong within the hour and right about nothing. Six hours is long enough that the answer is usable: it is a window you can open a window in.
If the forecast never holds that long inside the window, the page says so rather than inventing a time. That is a real answer too, and it is the one a person planning a week actually needs.
There are five levels, and they run All clear, In the air, Hazy, Heavy haze, Smokeshow. Each one is a concentration threshold, and the names never move: All clear means the same air in Fresno as it does in Toronto.
Every one of those names describes what the sky is doing rather than what you will smell, and that is deliberate. Fine particles scatter light long before anyone catches a campfire note, and smoke that has travelled for a day or more arrives with most of what you could have smelled already stripped out of it and the particles still there. Plenty of people have stepped outside into a genuinely smoky afternoon and smelled nothing at all. What they could do was see less far, which is why that is what these names track.
What changes city to city is what that air looks like out your window, and that is deliberate. The scale is anchored to visibility because visibility is the one reading you can take yourself without trusting a model, and you do not need an instrument to notice a mountain is gone. But ten miles of visibility is an ordinary clear day on the Chicago lakefront and an extraordinary one in the San Joaquin Valley, and in Seattle the top of the scale is Rainier standing out at roughly sixty miles. So each city page carries its own distance bands and its own named sightlines: the peak that flattens first, the skyline that merges into one mass, the hill you finally lose. Forcing one set of numbers on every city would throw away the strongest local signal there is.
Read the ladder on your city's page from the outside in. The furthest thing you can still resolve tells you which level you are in, and it tells you before any app does.
The size of that difference is worth stating plainly. A clean day in Seattle shows you Rainier at about sixty miles; a clean day in Detroit reaches Windsor across the river. Both are All clear. That is why each city page carries its own distances, and why this directory carries none: a number next to a city name gets read as today's reading, and the honest place for today's reading is the city's own page.
Most smoke in the eastern half of the continent is Canadian, and it is old by the time it arrives.
Out here two separate things decide your air: what arrives, and whether the ground you live on lets it leave.
This is the corridor where the haze is not always smoke, and saying so is most of the job.
Smokeshow is for informational and educational purposes only. It is not health, medical, or safety advice. Forecasts are model estimates and can be wrong, sometimes by a lot. Descriptions of what you might smell, see, or feel are generalizations, not predictions about your body. For decisions about your health, outdoor activity, or air quality safety, rely on official sources like AirNow.gov, the National Weather Service, and your local health authorities, and talk to a medical professional about your own situation.