Toronto’s air quality deteriorates as wildfires across Ontario produce drifting smoke and the region experiences extreme heat. Multiple reports say the city is repeatedly ranked among the worst places in the world for air pollution, with at times very poor air-quality readings affecting residents’ health. One outlet reports Toronto reaches the top spot or near the top on global pollution rankings, while another places Toronto among the worst globally—describing a Wednesday morning snapshot that ranks it behind only a few locations. The smoke is linked to forest fires in parts of northwestern Ontario, where the fires are active and conditions are producing haze that spreads beyond Toronto. Reports also note that the combined effects of wildfire smoke and high humidity contribute to hazardous conditions in the Greater Toronto area. Separately, smoke impacts air quality beyond Canada; one report notes smoke drifts into New York City and other areas. Health advisories and warnings are referenced as the air quality worsens, though the exact threshold levels are not detailed across all sources.