English: Smoke from wildfires in Western Canada darkened skies not only across that country, but dipped southward and eastward to cross the northeastern United States the North Atlantic Ocean on May 9, 2023. The Moderate Resolution Imaging Spectroradiometer (MODIS) on board NASA’s Aqua satellite acquired a true-color image of the massive river of smoke on that same day.

The smoke primarily originates from several intense fires burning in the provinces of Alberta and British Columbia. A few fires in southern Saskatchewan may also be adding to the gray skies. The west-to-east length of the plume was estimated at more than 3,770 kilometers (2,964 miles) using the NASA Worldview App measurement tools. The actual length travelled by the smoke was much greater, however, as it first was carried northward over the Northwest Territories and Nunavut before dipping southeast.

As of May 10, there were 81 wildfires burning in Alberta, according to the Alberta Wildfire Dashboard. A situation update by the government of Alberta on that same date counted 23 fires out of control and 17 being held and not expected to grow beyond projected boundaries given current weather conditions and resources. The report also states that there are 13 evacuation orders and 15 evacuation alerts in place, and the province recorded approximately 17,386 evacuees, 13,829 of which have registered at designated evacuation centers.

Early May is typically the start of the wildland fire season in Alberta, as snowmelt uncovers dead vegetation that can become fuel for fires. This year, an unusually hot and dry spring made it easier for fires to start and to quickly expand. Firefighting operations in the central portion of Alberta have benefited from a few days of light rain and cooler temperatures, but conditions are expected to get hotter and drier again within the next several days.