A few weeks ago a pall of smoke settled over our area, dulling the daytime sky. Visibilities in Wilmington, Dover and Philadelphia dropped to 1 to 3 miles on Sunday July 7 and Monday July 8.

As you may have heard, the smoke came from dozens of lightning-produced forest fires in Canada, east of James Bay in Quebec province, more than 800 miles away. In this satellite image, the heat signatures from the fires are red, while smoke is a light blue. The bright white on the right is a large, slow-moving, low-pressure system. Winds circulating counterclockwise around this storm directed plumes of the dense smoke to the south, and eventually some of it reached here. The smoke was mainly above 10,000 feet, but enough mixed down to the ground that you could, at times, smell a distinct odor.

Remarkably, the area of smoke remained intact even as it moved well out into the Atlantic, as seen in this image taken on Tuesday, July 9.