Calgary Air quality today

What is the Air Quality Health Index, and what does 10+ mean?

The Air Quality Health Index, or AQHI, gives a number from 1 to 10 for the health risk of local air ^[4]. The higher the number, the greater the risk ^[4]. During extreme events, such as a wildfire smoke event, it can reach 10+, which means very high health risk ^[4].

The index is worked out from three common pollutants: ground-level ozone, fine particulate matter and nitrogen dioxide ^[5]. Alberta Health Services says the biggest health risk in wildfire smoke comes from small particles called PM2.5, which are too small to see ^[6].

How bad was the wildfire smoke in 2023?

By the morning of September 4, 2023, Calgary had logged 476 smoky hours that year, according to Environment and Climate Change Canada ^[1]. The agency said it was the smokiest year on record for the city ^[1]. The previous record was 450 hours, set in 2018 ^[1].

A smoke hour is an hour when smoke cuts visibility to 9.7 kilometres or less, as measured by weather observers at stations such as international airports ^[2]. Since 1990, Calgary has averaged 73 smoke hours a year ^[2].

On the morning of September 4, 2023, Calgary's AQHI was rated 10+, or very high risk ^[1]. A Global Calgary meteorologist said dense smoke was moving in from northern British Columbia, pulled in by a high-pressure system over the province ^[1].

What happened in 2024 and 2025?

On the morning of June 11, 2025, the AQHI read 10+ in Calgary, Edmonton, Lethbridge and Red Deer ^[3]. Smoke from wildfires in northern British Columbia, Alberta and Saskatchewan covered most of the province ^[3]. Environment Canada issued air quality warnings, and several track meets in Calgary were cancelled ^[3].

From the start of 2025 to September 2, only 52 smoke hours had been recorded at Calgary International Airport ^[2]. Then a smoke plume covered the city on September 2 and 3, 2025, and the AQHI read 10+ early on September 2 ^[2]. An Environment and Climate Change Canada meteorologist said another plume from the Northwest Territories was expected to track through Alberta to Calgary ^[2].

The Calgary Region Airshed Zone, a group that runs air monitoring stations in and around the city, said its sensors showed a much less smoky 2025 than 2024, up to early September ^[2]. Its program manager said forest fires had affected Calgary a lot in 2024, with more PM2.5 exceedances than in 2025 ^[2].

Can an inversion trap pollution over Calgary?

Yes, though not often. In March 2018, Environment Canada issued a special air quality statement for Calgary because high pollution built up under a temperature inversion ^[8]. An inversion is when a layer of warmer air sits over heavier cold air near the ground ^[8].

Pollution normally rises away on air currents, but an inversion traps it at ground level ^[8]. Global News reported that this is not frequent in Calgary, but it sometimes happens as a chinook weather pattern is unfolding ^[8].

Where does Calgary's everyday pollution come from?

A University of Calgary study, reported in February 2018, mapped ozone, nitrogen dioxide and PM2.5 across the city ^[7]. It found pollution tends to be higher along main traffic corridors ^[7]. Deerfoot Trail, which runs north to south, is a major source of local pollution ^[7].

In summer, northeast Calgary had the most localized bad air ^[7]. That area has several traffic corridors, more industrial emitters and the international airport ^[7]. In winter, parts of south Calgary had some of the highest levels ^[7].

The researchers said Calgary's air quality is pretty good overall ^[7]. In an international comparison published in 2016, Calgary had lower PM2.5 levels than Montreal, Toronto and Edmonton ^[7].

Who is most at risk from smoke and poor air?

Alberta's health authority lists people with heart or lung disease, people aged 65 and older, pregnant people and children as being at higher risk ^[6]. So are people experiencing houselessness and people who do heavy outdoor work or sports ^[6].

Air pollution can irritate the lungs and airways, make it harder to breathe, and worsen heart disease and asthma ^[5]. On days when pollution is much higher than usual, even people outside these groups may notice symptoms ^[5].

How to protect yourself in Calgary

Check the AQHI before heading outside, and use its forecasts to plan your day ^[4]. At high risk, 7 to 10, people at risk should reduce or reschedule strenuous outdoor activity, and children and older adults should take it easy ^[4]. At 10+, everyone should reduce or reschedule strenuous outdoor activity, and children and older adults should avoid outdoor exertion ^[4].

When smoke is a problem, Alberta Health Services advises closing all windows and doors, including attached garage doors ^[6]. Use a portable air cleaner with a HEPA filter, and set up a cleaner-air room with the doors and windows closed ^[6]. If you have a forced-air furnace, a MERV 13 or higher filter may help lower smoke in your home ^[6].

Avoid things that make indoor air worse, such as wood-burning fireplaces, vacuuming and candles ^[6]. A well-fitted N95, KN95 or P100 respirator mask can filter fine particles, but not the gases in smoke ^[6]. If you have chest pain, shortness of breath or another emergency, call 911 ^[6].