Smoke from Canadian wildfires is engulfing much of the eastern and central United States and and is expected to continue for days.

(Reuters) -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.

The air quality is reaching dangerous levels in parts of the Upper Midwest and north central U.S., where copious amounts of smoke from wildfires in Canada are wafting south across the international border.