NYC, Chicago Air Quality Worsens on Canada Fire Smoke (2)

Wildfire smoke from blazes burning in the Canadian prairie has drifted across New York and Chicago, contributing to air-quality alerts that warn of breathing problems for children and older adults.

Environmental agencies in New York, New Jersey, Pennsylvania, Connecticut, New Hampshire and Maine issued safety advisories that are in effect from 11 a.m. local time Wednesday into late evening. The smoke is visible across the region as a high haze and has already blanketed the US Midwest, including Minneapolis and Chicago.

Smoke from Canadian wildfires envelope the downtown skyline in Chicago on June 3.

Photographer: Scott Olson/Getty Images

Chicago’s air quality index — which rises as pollution intensifies — reached 124 Wednesday, which is considered unhealthy ...