What to know about Canadian wildfires: How they started and where they are

TORONTO — Canadian officials are using one word to sum up Canada's wildfire season: Unprecedented.

From coast to coast, uncontrollable blazes in nine of the country's 13 provinces and territories have devoured millions of acres of forest, swallowed up hundreds of structures, forced more than 100,000 people from their homes and blanketed cities near and far from the flames in eerie clouds of toxic smoke.

Canada, whose 895 million acres of forest cover about a third of total land area, experiences wildfires every year. But this year's conflagrations have been particularly widespread, numerous and intense.

How bad is the wildfire smoke in your city? Use our tool to find out.

The outbreak of so many blazes across the country at this time of year is "not normal," officials here say — and the worst could be yet to come. If the rate of fire activity continues at its current pace, they said, the country will suffer the worst wildfire season in its recorded history.

"It is, in a word, sobering," Jonathan Wilkinson, Canada's natural resources minister, told reporters this week.

The amount of smoke pouring into the United States is also exceptional. Authorities from New York to Minnesota to Washington, D.C., have issued public health alerts and urged people to stay indoors and wear masks to protect themselves from potentially toxic fine particles in the air.

Here's what you need to know.

Latest news: Smoke from Canadian wildfires is spreading south over much of the Midwest, Ohio Valley, Northeast and Mid-Atlantic, bringing dangerous air pollution to the United States. Expect smoky conditions through the end of the week. Follow live updates on the wildfires and the impact on air quality.

Where the wildfire smoke is the worst: Satellite images show smoke covering the Northeast and extending into the Carolinas. Air quality in New York City and Philadelphia was particularly poor, and officials urged at-risk residents to wear high-quality masks outdoors. See how bad the wildfire smoke and air quality are in your area.

Air quality and your health: Breathing in wildfire smoke is bad for your health. The EPA uses a color-coded system to measure air quality, here's Here's an explanation of what Code Red, Code Purple and more mean. Learn how to protect yourself including which air filters and air purifers to choose for your home.