Smog, smoke and dry weather are combining to reduce air quality across the greater Vancouver area and the Fraser Valley, and officials expect the conditions to continue until Friday.
The lower Fraser Valley is the worst, according to Ken Reid, air quality planner for Metro Vancouver, the governing body of the greater Vancouver region, which issued an air quality advisory on Wednesday.
Officials call this a Level 5 alert on a scale of one to 10.
"Without the hot, sunny weather the smog wouldn't be developing. Without the hot, sunny weather you wouldn't see the limited mixing that we're getting in the valley and the buildup of pollutants," Reid said.
"And if the winds were coming from north to south, we wouldn't be getting the forest fires, either."
Air quality in the area is expected to deteriorate as more smoke from the Tyaughton wildfire near Lillooet drifts into the area, raising particulate levels in the atmosphere.
Residents are asked to cut back on activities that might increase air pollution, such as driving or burning open fires.
Dr. Tom Kosatsky of the B.C. Centre for Disease Control said how the reduced air quality affects people's respiratory system depends on each individual's health.
"You can get some degree of eye irritation, nose irritation and, for somebody who's already got asthma or a chronic chest condition, it can be very irritating. So their cough can get worse. They can wheeze more," he said.