Wildfires raging in the western United States are creating such intense heat that they are creating their own weather patterns, leading to the kind of cross-continental smoke flows that brought ashen skies to much of the East Coast this week.
There are dozens of infernos currently raging across 13 US states that have cumulatively burned an area larger than greater Los Angeles.
The Bootleg Fire in Oregon is believed to be to blame for the haze that descended on some residents of New York, Philadelphia, Boston and Washington DC on Tuesday and Wednesday.
The smoke is being brought across the United States by pyrocummulus clouds. These towering ash-filled clouds are created when the extreme heat from wildfires force air to rapidly rise, and as the flames consume trees and plants in their path, the water inside them evaporates into the rising air.
Smoke particles join with the added moisture in the atmosphere to create menacing thunderclouds that can produce their own lightning, tornadoes, and force the wind to blow around them.
“Normally the weather predicts what the fire will do. In this case, the fire is predicting what the weather will do,” Marcus Kauffman, a spokesman for the state forestry department told the New York Times.
Meteorologists say the pyrocummuls clouds were carried 3,000 miles eastwards from southern Oregon, through the Great Lakes district and on to the East Coast on high-level winds.
The smoke clouds had been met and enlarged by closer fires in the Canadian provinces of Ontario and Manitoba.
Smoke travelling across the US to the East Coast was not especially rare, according to the Department of Environmental Conservation.
But this week’s smoke flows hung lower than usual, extending to ground level in some places.
Lunchtime thunderstorms in New York City on Wednesday brought some relief from the lower air quality.
But the unpredictable nature of the pyrocummulus clouds, and changeable weather patterns in the west, mean the poor air quality could return within days.
Wildfires burning out of control across the Western United States brought smoke-filled skies to New York City and Washington DC on Tuesday.
The National Weather Service (NWS) said smoke and haze from the Bootleg Fire in Oregon that had drifted across the Great Lakes region had reached the Eastern Seaboard.
“This will filter the sunshine here throughout the day today,” the NWS said on Twitter.
The smoke blankets partially blocked the sunrise in New York on Tuesday, weather watchers reported, and when the sun eventually became visible it had a distinctive reddish hue.
New York State’s Department of Environmental Conservation issued a rare air quality alert for parts of upstate New York including the Finger Lakes and Rochester.
It recommended older adults, young children, and anyone with underlying conditions should stay indoors.
Similar warnings were in effect for much of Canada, as well as from Vermont to northern New York state until midnight Tuesday, the NWS said.
The smoke, which stretched as far south as Washington DC, was likely to remain visible until a cold front sweeps through later in the week.
Montana and Idaho account for 35 of the fires, which are aided by a heatwave that has brought searing temperatures and dangerous conditions for firefighters.
The largest single blaze, the Bootleg Fire, has scorched around 350,000 acres, or 530 square miles, of forest and grasslands, with thousands of firefighters battling through extreme forms of weather generated by the blaze.
As the smoke builds, it becomes caught up in weather systems and transported across the country.