Even though Vancouver skies appear to be quite smoky, air quality remains "moderate"

This morning, it was difficult to tell whether it was the clouds or the smoke from B.C. wildfires that was most responsible for the eerie look of the sky over Vancouver.

The image above was taken in Kitsilano, showing the sun trying to peek out just after 10 a.m. through the smoke and clouds.

The Air Quality Health Index has the northwestern section of Metro Vancouver at a five ("moderate") rating today.

This means the general population does not need to modify its usual outdoor activities unless they experience coughing or throat irritation.

The at-risk population—including those with heart or breathing problems—should consider reducing or rescheduling strenuous activities.

The AQHI is expected to remain at five tomorrow in the northwestern part of the region.

However, will shoot up from four to seven ("high") in the northeastern and southeastern parts of Metro Vancouver.

Ratings from seven to 10 are usually because of high concentrations of smoke particles of 2.5 micrometres or less in diameter.

Metro Vancouver issued an air quality advisory yesterday for the Lower Mainland and Fraser Valley.

"Concentrations of ground-level ozone may also reach advisory levels in eastern parts of Metro Vancouver and the Fraser Valley due to hot weather conditions," the advisory noted.

It added: "Ground-level ozone is not emitted directly into the air. It is formed when nitrogen oxides (pollutants emitted when fuels are burned) and volatile organic compounds (emitted from solvents) react in the air in the presence of sunlight. The highest levels of ground-level ozone are generally observed between mid-afternoon and early evening on summer days."