Start with the Canadian air-quality product
The Air Quality Health Index explanation describes how Canada reports air pollution through the AQHI. It is not the same index as the US AQI. Copying a number between the two legends, or assuming that identical colours carry identical definitions, loses the meaning of the original report. Read the Canadian location, reporting time and product name before comparing a cross-border map.
A useful comparison between Vancouver and Seattle therefore begins with two labelled products, not two unlabelled numbers. Preserve the original scale on each side of the border. For Canadian locations, check the reporting service offered for that community; do not assume that every provincial product has the same interface or coverage. The Info-Smog service explains the distinction between its southern Quebec coverage and AQHI services.
Separate a smoke forecast from a local reading
Environment and Climate Change Canada's air-quality model forecast maps show projected pollutant concentrations and wildfire-smoke movement. The map's valid hour is essential: a frame for tomorrow is not an observation of the air outside now. Check which field is selected, because a smoke-related PM2.5 map, total PM2.5 map and averaged map describe different quantities. Keep the forecast issue time separate from the displayed hour.
When browsing a sequence, compare the same product at successive valid times. Do not compare the darkest patch of an hourly map with the daily average from another map and call it a sudden improvement. A forecast is a model output, while a station or local report uses its own reporting method. Disagreement deserves a check of time, quantity and coverage before any conclusion about which map is wrong.
A practical cross-border reading workflow
First identify the Canadian community and open its official current air-quality report. Next inspect the model forecast for the same area and the time window you are researching. Finally use fire information to understand the broader context. This sequence keeps local reporting, future smoke transport and the location of a fire from being treated as interchangeable evidence.
The PocketWorld Canadian wildfire guide explains satellite detections and reported fires. PocketWorld does not reproduce the full AQHI network or the complete FireWork forecast viewer. Its available disaster records should be read with their provider and freshness labels. For health decisions, use the official guidance attached to the local product rather than this explanatory article. If you share a comparison, label both indices, both timestamps and whether either image is a forecast. That makes the result useful to someone who did not see the original map controls.
Data sources
References are linked beside the explanations above. This evergreen guide does not report current incidents.