Wildfires across the western United States and Canada have put millions of people under air quality alerts, as thousands of firefighters battle the flames, including the largest wildfire in California this year.

Thousands of firefighters battling a wildfire in northern California are getting some help from the weather just hours after the blaze exploded in size, scorching an area larger than Los Angeles.

Thousands of firefighters are battling a wildfire in northern California that exploded in size — one of several blazes tearing through the western United States and Canada amid dry, hot and windy conditions.