BOSTON – Smoke from hundreds of wildfires burning across Canada has polluted skies and reduced air quality across large portions of the Midwest and Northeast in recent days, but forecasters expect conditions to begin improving on Wednesday as shifting winds help disperse the haze for millions along the Eastern Seaboard.

The Canadian Interagency Forest Fire Centre reports that nearly 800 fires are currently burning nationwide, with over 200 considered out of control.

With several larger blazes located in hard-to-reach areas, officials warn that some of these fires could continue for weeks – if not longer – due to limited accessibility and abundant fuel.

Northerly to northwesterly winds over the weekend and into the early part of the week helped push the wildfire smoke south into the United States, triggering air quality alerts from Minnesota to Maine.

CANADIAN WILDFIRE SMOKE SMOTHERS SKIES FROM MIDWEST TO NORTHEAST AS AIR QUALITY PLUMMETS FOR MILLIONS

At times, the smoke was dense enough to cause visibility reductions and even disrupt air travel. 

Flights into and out of Boston’s Logan International Airport were impacted on both Monday and Tuesday due to the thickness of the smoke layer.

Cities including Detroit, New York City and Chicago ranked among the top 10 most polluted cities in the world during the week, based on Air Quality Index readings.

The unhealthy levels prompted warnings for millions of residents to limit outdoor activity, especially those with respiratory or cardiovascular conditions.

Most alerts, particularly along the I-95 corridor, are expected to be lifted by Wednesday, as a noticeable shift in weather patterns brings in a southerly and onshore flow across the region.

The more pronounced wind shift is expected to push much of the smoke away from the surface, allowing air quality to gradually improve. However, enough smoke is expected to remain in the upper levels of the atmosphere to impact the vibrancy of sunrises and sunsets.

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Despite short-term improvements, smoke-related impacts will remain a concern, with hundreds of fires still burning out of control north of the border and throughout parts of the western United States.

The threat of additional smoke plumes remains possible, especially on days when the prevailing wind pattern shifts back to the north or northwest.

The FOX Forecast Center says it is monitoring weather conditions across the Canadian provinces of Saskatchewan, Manitoba and Ontario, where rainfall totals could reach several inches over the next week.

While the precipitation could help reduce fire activity by damping brush, it also introduces the risk of lightning, which is one of the most common ignition sources for flames and wildfires.