Smoke from wildfires burning in three Canadian provinces covered about a third of the U.S. on Wednesday, forecasters said, but had little effect on air quality except in New England and parts of New York state and the Midwest.

Smoke from Canadian wildfires continues to worsen air quality across the Midwest and parts of the Northeast. The Canadian wildfires have been burning since mid-May and, as of Wednesday, June 4, there are 203 active fires, according to the Canadian Interagency Forest Fire Centre. Of those fires, only 70 are under control.