Forest fires in Quebec have partially resulted in a smog advisory for the city of Hamilton.

The Ministry of the Environment issued an advisory today for Hamilton, as well as Halton-Peel, Toronto and York-Durham. Hamilton has one of the highest readings in the province.

"East to northeasterly flow of polluted air from forest fires in Quebec is resulting in high smog levels over eastern and parts of southern Ontario today," the advisory reads.

Hamilton's air is currently rated as poor, with particularly high readings downtown. The advisory will remain in effect until further notice.

A smog advisory is related to the air quality index (AQI), which rates how clean the air is. Higher AQI numbers mean high health risks.

A smog advisory is issued when the AQI is expected to reach 50 in the next 24 hours. Downtown Hamilton currently sits at 61, while Hamilton Mountain is at 50 and Hamilton west is at 53.

Smog is made up of a complex mixture of air pollutants that may or may not be visible. Its main ingredients are ground-level ozone and fine particular matter.