Sri Lanka, Aug. 4 -- Hazy skies hung over parts of the midwest and northeastern U.S. on Sunday, caused by smoke drifting across the border from hundreds of wildfires in Canada.

Canada is experiencing its second worst wildfire season on record, according to government data, with almost 4,000 fires recorded already this calendar year.

Smoke coming across the border has affected air quality in several U.S. states.

This weekend, air quality reached concerning levels across Wisconsin, Michigan, and Minnesota. Parts of Illinois and Indiana are also under air quality alerts. People in New York, Vermont, New Hampshire, and Maine are also being advised to limit outdoor activity due to pollution from the smoke.

National Weather Service Lead For...