Data collected by the European Union's Copernicus Atmosphere Monitoring Service found smoke from the fires had traveled 8,000 kilometers (almost 5,000 miles) through the atmosphere to Britain and other parts of northern Europe.
RELATED | Smoke from West Coast fires travels cross-country to New York City
The European Centre for Medium-Range Weather Forecasts, which operates some of the Copernicus satellite monitoring systems, said the fires in California, Oregon and Washington state have emitted an estimated 30.3 million metric tonnes (33.4 million tons) of carbon.
"The scale and magnitude of these fires are at a level much higher than in any of the 18 years that our monitoring data covers, since 2003," Mark Parrington, a senior scientist and wildfire expert at Copernicus Atmosphere Monitoring Service, said.
Parrington said the smoke thickness from the fires, known as aerosol optical depth or AOD, was immense, according to satellite measurements.
"We have seen that AOD levels have reached very high values of seven or above, which has been confirmed by independent ground-based measurement," he said. "To put this into perspective, an AOD of one would already indicate a lot of aerosols in the atmosphere."