Wildfires are burning longer and more frequently in some northern latitudes due to climate change. Wildfires are often triggered by lightning, intentional land clearing, or human-caused accidents. Higher than normal temperatures and drier than normal conditions are further exacerbating conditions.
The largest wildfire currently burning in the United States is the Bootleg Fire in south-central Oregon near the city of Bend. Nearly two weeks after it started, Bootleg Fire has burned 467 square miles (1,209 square kilometers), roughly the size of the cities of Los Angeles or Phoenix.
This video shows a satellite view of the Bootleg Fire in southern Oregon. The white billowing clouds that erupt from the area are pyrocumulonimbus (pyroCb) clouds.
The recent heatwave that settle over much of the Pacific Northwest and Canada also created conditions that triggered multiple wildfires in Canada. On June 29, 2021, Lytton, British Columbia reached 121°F (49.6°C), the highest temperature ever recorded in Canada on any date.
By late June, more than 40 wildfires erupted across British Columbia. By July 8, the number had risen to more than 200 active fires across the Canadian province, with 15 of them classified as “wildfires of note” (especially large fires, or fires that threaten public safety).
This satellite image shows the formation of pyrocumulonimbus (pyroCb) clouds which can be seen as bright white areas above the McKay Creek fire and the Sparks Lake fire. Convection and heat rising from a fire create these towering clouds.
Since the beginning of July 2021, plumes of smoke have spread throughout the skies of Ontario as a result of a group of large wildfires burning along the border with Manitoba.
This satellite image from NASA shows parts of Minnesota, North Dakota, and South Dakota that are now experiencing widespread smoke moving into the region from Canada. The smoke has prompted the Duluth office of the United States National Weather Service to issue an air quality alert for parts of northeastern Minnesota.
The smoke from the wildfires burning in Canada and the Pacific Northwest is so strong that parts of the Midwest and the East Coast are experiencing unhealthy air pollution levels from smoke. Smoke from 3,000 miles away has traveled to these regions of the United States and weather stations and news stations in the area were reporting smokey and hazy conditions on July 20, 2021.
This screenshot from PurpleAir, a crowdsourced Internet of Things app which maps air quality sensors across the United States, shows how parts of the United States are experiencing lower air quality due to smoke from these fires.
Wildfires in Arizona
Drought and extreme heat has also led to dozens of wildfires being triggered in part by dry lightening striking the parched landscapes of Arizona and New Mexico.
On June 21, 2021, NASA’s Aqua satellite’s Moderate Resolution Imaging Spectroradiometer (MODIS) captured this natural-color image of smoke streaming from several large fires in Arizona.