Smoke from wildfires burning in Canada is drifting into the United States, causing hazardous air quality conditions in many parts of the country.
The Environmental Protection Agency (EPA) has issued air quality alerts for much of the eastern United States, warning that the smoke can cause respiratory problems, such as asthma and bronchitis.
People with respiratory problems are being urged to stay indoors and avoid strenuous activity.
The wildfires in Canada are the result of a combination of factors, including hot, dry weather and high winds.
The wildfires are expected to continue burning for several days, and the smoke is expected to continue drifting into the United States.