Wildfire smoke blankets cities across North America.

New York City's official emergency notification system, NotifyNYC, has warned that air quality conditions may worsen on Saturday night due to smoke from Canadian wildfires. The advisory has urged residents, especially those with respiratory or heart problems, older adults, and children, to limit outdoor activity as much as possible. The city's Air Quality Index measures pollution on a scale between zero and 500, with anything above 150 considered to be unhealthy. The deteriorated conditions were caused by smoke from some 250 wildfires in Canada over the past several days.