May marked the early start of the wildfire season in the Canadian provinces of Manitoba and Saskatchewan. The fierce fires in the vast forests and prairies worsen local air quality due to the high levels of particulate matter and threaten the US East Coast with heavy smoke – and they also have a global impact. Data from the EU’s Copernicus climate service for the last few days of May showed smoke particles moving from the Americas across the Atlantic to Western Europe. More of these soot clouds are expected on the US East Coast over the next few days, and later in Europe.