Goddard Earth Observing System (GOES) model of smoke from wildfires in west and central North America spreading eastwards across the continent on 21st July 2021. Colours correspond to the concentration of black carbon particles, or soot, in the air. Blue areas contain, no black carbon, orange areas have a mass density of 6 milligrams of black carbon per metre squared, red areas a density of 8 milligrams of black carbon per metre squared and dark red areas a density of 10 milligrams of black carbon per metre squared. The smoke is travelling over 3000 kilometres, causing poor air quality and visibility in east coast cities, including New York City.