Canadian wildfire smoke chokes Toronto, threatens US cities

TORONTO/NEW YORK — Toronto's air quality ranked the worst among major cities globally on Wednesday as wildfire smoke from northwestern Ontario blackened skies and spread into the northeastern United States, prompting health warnings and calls for residents to limit outdoor activities.

Wildfires are raging through sparsely populated areas hundreds of miles from Toronto and sending smoke over a wide area, although they are not directly threatening cities.

Environment Canada reported an Air Quality Health Index reading of 10+, classified as "very high risk," for Toronto, while forecasts suggested hazardous conditions could persist through Thursday night.

New York City began feeling the effects days before neighboring New Jersey is scheduled to host the World Cup final on Sunday.

Local authorities issued an alert as air quality reached an unhealthy level and urged residents to reduce strenuous outdoor activity and take extra breaks if they are outside on Wednesday and Thursday.

The National Weather Service said smoke could linger into the end of the week.

"We probably haven't seen the worst ...