Calgarians woke up to a hazy skyline Thursday morning as smoke drifted in from forest fires in B.C. and Alberta. 

The smell of smoke remains in the air in Calgary, but Environment Canada's air quality health index for the city has been downgraded to "low risk." 

However, the national weather agency has issued "special air quality statements" many parts of central Alberta, including Calgary.

That means people prone to respiratory problems should avoid outdoor activities if the smoke triggers a reaction.

There is a total of 18 wildfires burning in Alberta — three are out of control, six are being held and nine are under control. 

Most are in the northern part of the province.

Since April 1, Alberta has recorded 840 wildfires which have burned 14,277 hectares.

Because of the hot dry conditions, officials have issued a fire advisory for the Calgary area.

No new burn permits will be issued, but existing ones are still valid.

The wildfire hazard status is now extreme.

In B.C., there more than 120 forest fires currently burning. The Northwest Territories has about 160.

Air quality health index

CBC Calgary weather specialist Craig Larkins tweeted this summary of the air quality health index in five Alberta areas. (@Craig_Larkins/Twitter)