Guide to Environment Canada's Air Quality Health Index (AQHI) 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 two days, and provides other related health messages. To get the latest AQHI forecast for a specific location, click on one of our regional maps.
Table of Contents
- Air Quality Health Index Forecast Bulletins
- Air Quality Elements and when they are included in the forecast
- Special Air Quality Statement
- Information on the expanded AQHI program in Ontario
Air Quality Health Index Forecast Bulletins
- When are forecasts issued?
- What time period does the forecast cover?
- How are forecast regions defined?
- What information is included in the forecast?
- Sample Forecasts
- Forecast Revision
The Air Quality Health Index (AQHI) forecast bulletin provides both a quantitative and qualitative description of the air quality health index expected within the next two days (refer to Table 1 for exact time periods).
The AQHI is a personal health protection tool providing individuals with air quality conditions and concrete measures that they can take to reduce the risk associated with air pollution. The AQHI is calculated based on the relative risks of a combination of common air pollutants which are known to harm human health. These pollutants include Ozone (O3) at ground level, Particulate Matter (PM2.5/PM10) and Nitrogen Dioxide (NO2).
When are forecasts issued?
The AQHI forecast bulletins are issued two times per day: the first one is issued between 5:00 a.m. and 6:00 a.m., and the second one is issued between 4:00 p.m. and 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|
|5:00 a.m. – 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 Midnight (12:00 a.m.)|
|4:00 p.m. – 5:00 p.m.||N/A||Issue time to 6:00 a.m.||6:00 a.m. to Midnight (12:00 a.m.)|
Below, the same information can be seen along a timeline:
5:00 a.m. – 6:00 a.m. forecast issue
4:00 p.m. – 5:00 p.m. forecast issue:
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?
Days 1 and 2:
The AQHIforecast bulletin will always contain the following standard elements (see Air Quality Elements for further details):
- Maximum Air Quality Health Index (AQHI)
- Health Risk Category
- AQHI Scale
SAMPLE forecast (Weather.gc.ca)
- The Navigational toolbar that allows you to quickly link to other meteorological products and educational resources offered by Environment Canada; from radar and satellite images, marine information to fact sheets and Frequently Asked Questions.
- The Air Quality Health Index scale shows you the AQHI range and corresponding risk category.
- The Current Conditions displays AQHI information for the location chosen, along with the time and date that the information is valid.
- The 24 hour history provides the AQHI and risk category for the past 24 hours.
- The At-Risk and General Populations text provides information to the current AQHI value for each group.
- The Health Message Tab provides you with the health information for each risk category for both the At-Risk and General populations.
- The Forecast Maximums provides the complete AQHI forecast. See SAMPLE regular forecast for a more detailed explanation of our text forecasts.
- The Next 18 hr provides an hourly forecast of the AQHI for the next 18hr
- The Who is at risk? text provides information about risk groups and where to go for further information.
- The Did you know…? text provides facts related to air quality.
- The Initiative information provides the names of Environment Canada, Health Canada and the provincial partners.
SAMPLE regular forecast (text bulletin)
Example: Sample Regular Forecast
The numbers provide a description of the forecast text.
FLCN21 CWHX 042000
Air Quality Health Index forecast for Nova Scotia issued jointly by Environment Canada and Nova Scotia Environment and Nova Scotia Health Promotion and Protection at 5.00 pm ADT Monday 4 May 2009 for tonight and Tuesday. The next scheduled forecast will be issued at 6.00 am Tuesday.
- Tonight...Maximum Air Quality Health Index 2 or low risk.
Tuesday...Maximum Air Quality Health Index 1 or low risk.
- Air Quality Health Index Scale:
1-3 Low health risk
4-6 Moderate health risk
7-10 High health risk
Above 10 Very high health risk
- For more information, consult Air Quality Health Index website
- This text is called the “title block”. It indicates the forecast area, the date and the time for which the forecast is. It also indicates when the next forecast will be issued.
- The forecast region name(s) is the full name of the region(s) or metropolitan area(s) for which the forecast is issued.
- The forecast text is broken into distinct periods (i.e. today, tonight, tomorrow) for ease of readability. See Table 1 for information on the times associated with the different periods.
- The Air Quality Health Index scale shows the AQHI range and corresponding risk category.
- Link to more information.
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 elements and when they are included in the forecast
Maximum Air Quality Health Index (AQHI)
Included in the forecast for Day 1 and 2? - Yes
Indicates the maximum AQHI numerical value and category
Day 1 and 2: The maximum AQHI value is the only element in the forecast and will represent the maximum AQHI value over each part period, today, tonight and Day 2.
- 1-3: Low risk
- 4-6: Moderate risk
- 7-10: High risk
- Above 10: Very high risk
Special Air Quality Statement
The purpose of the Special Air Quality Statement is to explain air quality situations that cannot be adequately described in the Air Quality Health Index forecast bulletin.
- To highlight significant events like forest fire smoke that is not impacting the AQHI value.
- To describe other air quality pollutants that are not included in the AQHI calculation such as odour producing pollutants like sulphur dioxide, or pollutants that may restrict visibility.
Information on the expanded Air Quality Health Index (AQHI) program in Ontario
Environment Canada and the Province of Ontario are working together to bring the Air Quality Health Index (AQHI) to more locations in Ontario. Details follow:
- Air quality alerts: Environment Canada and the Province of Ontario jointly issue air quality alerts. These will be posted on the Province of Ontario website and Environment Canada’s Weatherwebsite.
- Air quality measurements: The AQHI is based on measurements taken at air quality monitoring stations managed by the Province of Ontario. Information on the stations, with current air quality measurements, can be found on their website.
- AQHI forecast schedule: As the AQHI program expands in Ontario, there will be differences in the format of the daily forecast, until Environment Canada starts its province-wide AQHI forecasting in 2016.
|Daily Forecast schedule||Environment Canada||Province of Ontario|
|Morning Forecast (issued at 5:00 -6:00 am local time)||Maximum AQHI for today, tonight and tomorrow||Maximum AQHI for today and tomorrow|
|Afternoon Forecast (issued at 4:00 -5:00 pm local time)||Maximum AQHI for tonight and tomorrow||Maximum AQHI for today and tomorrow|
- Date modified: