Edmonton Marathon organizer John Stanton knows there's something in the air, and he doesn't like it.

Stanton has been keeping an eye on the acrid grey smoke from B.C. forest fires that is blanketing Alberta and has drifted into Saskatchewan, Manitoba and was creeping into northwestern Ontario by Friday night.

He is wondering how it will affect the 4,000 people expected to run in Sunday's race.

"We've added additional medical people and we've also added additional equipment," Stanton said Friday. "We've been, almost hourly, talking to Alberta Health and monitoring the air quality conditions."

Health officials say there is reason for concern. On Thursday, Alberta's chief medical officer issued a warning that urges people with chronic lung conditions to stay indoors and asks people with healthy lungs to avoid strenuous activity.

The smoke can cause severe trouble for people with conditions such as asthma, bronchitis or emphysema.

The Saskatchewan government issued a similar warning Friday.

"People who are at higher risk, including persons with asthma and other respiratory and heart conditions should consider staying indoors with the windows closed to reduce their exposure to the outdoor air when the air quality is even moderately bad," Dr. Saqib Shahab, Saskatchewan's deputy chief medical health officer, said Friday in a release.

"Even otherwise healthy people should also avoid any vigorous outdoor physical activity while there is heavy smoke in the air."

There were 178 sizable fires burning across British Columbia Friday. Residents from 728 properties had been evacuated and a further 1,138 homes were on evacuation alert.

The large fires and slow winds have created one of the most wide-ranging smoke problems in recent memory on the Prairies. The smoke has drifted more than 1,300 kilometres.

"There's pretty much a westerly flow at the surface that is pushing (the smoke) east across the Prairies," said Sandy Massey, an Environment Canada meteorologist in Winnipeg.

"There's not a lot of rain to help scour any of that out and not any strong winds to really change that pattern right now."

Some relief was expected for the weekend and those in Toronto need not worry -- the smoky air won't travel that far east, says Environment Canada meteorologist Gary Dickinson.

Winds are expected to pick up Saturday and Sunday and shift to the northwest.

Until that happens, people are trying their best to adjust to the smoke. Some of the volunteers at Edmonton's Fringe theatre festival wore face masks to help filter the air while a cycling club cancelled a group ride planned for Saturday.

For Prairie folks used to a clear blue sky, the smoke has come as a shock.

"There are parts of this city where you can't see across the street," said Deb Steele of the Lung Association of Alberta.

"It limits their proposed activities and it limits their daily life," she said. "We advise them to pay attention to any tickle in the back of their throat, wheezing, chest tightening, coughing and shortness of breath."

As for the Edmonton Marathon, Stanton said Sunday's race is on, but the runners will be advised to take precautions.

"We'll be reading to the runners a precautionary statement prior to the start of the event to ensure they're briefed on the concerns."