Guide to Air Quality Health Index forecasts
The Air Quality Health Index (AQHI) was developed, in partnership with Health Canada, the provinces and other local partners. It is a public information tool that provides daily forecasts about air quality levels. It lists, on a scale from one to 10, the health risks associated with certain air pollutants known to be harmful to human health. Using the scale, Canadians can be better prepared to deal with air pollution and take the appropriate steps to limit their exposure.
The AQHI is forecasted twice daily for certain locations across Canada; it also predicts maximum AQHI values over the next three days, and provides other related health messages. To get the latest AQHI forecast for a specific location, visit your local AQHI conditions.
When are forecasts issued?
The AQHI forecast bulletins are issued two times per day: the first one is issued at 6:00 a.m., and the second one is issued at 5:00 p.m. local time.
What time period does the forecast cover?
The following table indicates the time period that the forecast covers for each of the two forecast issue times. The issue times of the bulletin are within a half-hour of the times indicated above.
Table 1 : Time periods for the AQHI forecast bulletins
| Forecast Issued at: | Today | Tonight | Tomorrow | Tomorrow night | Next Day |
| 6:00 a.m. | 6:00 a.m. to 6:00 p.m. | 6:00 p.m. to 6:00 a.m. | 6:00 a.m. to 6:00 p.m. | 6:00 p.m. to 6:00 a.m. | N/A |
| 5:00 p.m. | N/A | Issue time to 6:00 a.m. | 6:00 a.m. to 6:00 p.m. | 6:00 p.m. to 6:00 a.m. | 6:00 a.m. to 6 p.m. |
How are forecast regions defined?
Forecast regions are closely aligned with cities, communities and municipal boundaries. Local factors such as terrain, land cover and population patterns were used to define these regions. The names of the forecast regions generally correspond with those of the most prominent communities or geographic regions. The names were chosen on the basis of how well they represent the area covered by the region. All official place names can be found in the Canadian Geographical Names Database.
What information is included in the forecast?
The AQHI forecast bulletin will always contain the following standard elements:
- Maximum Air Quality Health Index (AQHI)
- Health Risk Category
- AQHI Scale
Forecast revision
The Air Quality Health Index forecast is amended when forthcoming conditions are expected to be significantly different from those originally forecasted, but only in a way that public safety is at risk, or when public inconvenience will be extensive. Making an amendment is always at the forecaster’s discretion. An amendment to the Air Quality Health Index forecast bulletin is initiated when the following criteria have been satisfied:
- If the AQHI value rises or falls two or more index values on the AQHI scale; and
- If it is expected to stay at that value for four hours or more.
Air Quality Warnings
We issue Air Quality Warnings when air pollution is expected to rise or is already high. This can happen because of wildfire smoke, urban pollutants, or industrial activity, which can increase harmful substances in the air like fine particles (PM2.5), ozone, or nitrogen dioxide.
The Warnings give you information to help you protect your health. They explain what’s happening, what the impact might be, and what actions you should take.
Air Quality Warnings are colour-coded (yellow, orange, or red) based on possible risks. The Air Quality Health Index (AQHI) helps us determine when to issue a warning, and what colour to use. Learn more about colour-coded alerts.