Pyrocumulus clouds erupt from a massive wildfire near Buffalo Lake, as seen by the Moderate Resolution Imaging Spectroradiometer aboard the Aqua satellite on August 05, 2014. (NASA)

While the western U.S. is experiencing a relatively tame wildfire season, the Northern Territories of Canada is in the midst of one of its worst fire seasons on record.

In a rare event, a NASA satellite captured the pyrocumulonimbus clouds of an intense fire burning near Buffalo Lake. NASA writes:

While fire clouds occur with some regularity, it’s rare for Aqua to capture images of such mature pyrocumulus clouds. Because of their orbits, Terra always crosses the equator in the morning and Aqua always crosses in the early afternoon (local time). Since pyrocumulus clouds are most developed in the late afternoon or evening, they tend to look small and immature in MODIS imagery.

Scientists monitor pyrocumulonimbus clouds closely because they can inject smoke and pollutants high into the atmosphere. As pollutants are dispersed by wind, they can affect air quality over a broad area affecting areas far from the fire site. Currently large portions of the Northwest Territories are under a health alert due to the smoke resulting from these wildfires.

As we wrote on Tuesday, pyrocumulus clouds form when intense heat at the ground causes air to rise rapidly. This usually happens in the event of a wildfire or volcanic eruption. The clouds themselves form in the way that all clouds do — as the air rises, water vapor condenses into tiny droplets, which form the cloud. While typical cumulus clouds appear puffy and white, pyrocumulus can take on a grey appearance due to the ash and smoke within the cloud. In the case of exceptionally strong updrafts, pyrocumulonimbus clouds are possible, which can produce rainfall and lightning.

352 fires have been ignited so far in 2014 in the Northwest Territories, which have burned around 7 million acres. For comparison, by August 7, 2013, there were 228 fires with only about 900,000 acres burned.  1.8 million acres have been burned so far in 2014 in the western U.S.

Active fires (orange flames) burning in the Northwest Territories on Thursday. Black dots signify extinguished fires. Image captured from Northwest Territories Environment and Natural Resources website. (

On Tuesday we posted about stunning pyrocumulus clouds that were photographed by the Oregon Air National Guard. Those clouds were generated by the Oregon Gulch fire, which as of Thursday has been completely surrounded by firefighters as they attempt to contain the blaze.