Canadian wildfire smoke has arrived in DC yet again, and could get worse

Wildfires burning in parts of Minnesota and western Ontario, Canada, are sending thick plumes of smoke toward the eastern United States.

Dense smoke has already spread into parts of the Great Lakes and Northeast, reducing air quality and turning the sky eerie shades of orange and red. Here in the DC area, lower concentrations of smoke arrived Tuesday but remained high enough in the atmosphere that they didn't affect air quality.

That could change. While the thickest smoke is expected to stretch from northern Wisconsin to Massachusetts on Wednesday, it should sink south into Pennsylvania Wednesday night into Thursday. Around that time, smoke concentrations may increase modestly in the DC area, especially across northern Maryland.

The period of greatest concern locally will be late Thursday night into Friday, when winds from the northwest may direct the plume directly through the Mid-Atlantic.

• Reduced air quality: The smoke may become thick enough to increase fine-particle pollution near the ground, although it's too soon to know by how much.
• Smoky odor: The air may smell like a campfire.
• Reduced visibility: Hazy skies could limit how far you can see.
• Slightly cooler temperatures: Thick smoke can block some sunlight, trimming afternoon highs by a couple of degrees.
• More vivid sunrises and sunsets: Smoke particles scatter sunlight, often producing especially vibrant oranges and reds.

The last major incursion of Canadian wildfire smoke into the DC area occurred in June 2023. During that episode, the region experienced its worst smoke pollution on record, with two days of widespread unhealthy air and surreal, Mars-like skies.

It's too early to know whether this event will approach that level, but we'll be watching closely and provide updates as the forecast becomes clearer.

Even the thin veil of smoke overhead Tuesday evening helped produce an especially colorful sunset. See some photos below: