Wildfire smoke degrades air quality in swaths of Ontario, with Toronto ranking among the worst in the world on Monday.

At least four firefighters have been injured over the last week while battling three wildfires in Northern California forests that are burning amid extreme heat in steep, bone-dry terrain, fire officials said Monday.

The Dragon Bravo Fire has destroyed dozens of structures and a water treatment facility, and the White Sage Fire, located in Kaibab National Forest, has forced hundreds to evacuate.

With a pump and a sprinkler, one Palisades resident thinks he can help Californians protect their homes from fire. Experts disagree on whether it could work.

Wildfires have scorched hotspots in several Mediterranean countries this month, with blazes forcing thousands of people into lockdown in Catalonia in Spain, and encroaching on France's second-biggest city of Marseille.

Crews are fighting five western slope blazes, including one at the Black Canyon of the Gunnison. See the latest map of the Colorado fires.

The Chicago area recorded ozone levels of 156 late Monday afternoon. Levels above 100 are considered unhealthy. Residents with respiratory issues, children and the elderly are advised to stay indoors and limit exposure to air outside until Tuesday evening.

More than two hundred firefighters tackled three separate grass fires in east London on Monday evening. Some residents in Dagenham were asked to temporarily leave their homes after eight hectares (20 acres) of grass, shrubland and trees, fences and garden furniture caught alight near Beam Parklands.