Environment Canada says poor air quality in central and southern British Columbia due to wildfires in the United States is expected to improve over the coming days.
Ground-level smoke could persist in some regions, including Metro Vancouver, at least until Friday, when showers are expected into Saturday.
Anyone with chronic underlying health conditions or respiratory infections, including COVID-19, is advised to limit or postpone physical activity outdoors until conditions improve.
Canada Post says there may be delays in mail delivery in parts of B.C. due to concerns about workers' health as smoke from forest fires in Oregon and Washington state wafts north.
Those areas include Cloverdale, Delta, parts of Metro Vancouver and New Westminster, where conditions were worsened by a fire at a timber wharf that has continued to smolder since Sunday.
Full mail delivery has been restored to other parts of province, including Abbortsford, Nelson, Trail and Penticton.