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New York City 's Statue of Liberty sits behind a cloud of haze from the western wildfires. Photo: Spencer Platt/Getty Images

Smoke from the wildfires engulfing the U.S. West and Canada and carrying harmful air pollution has triggered air quality alerts in the Upper Midwest and East Coast cities including New York, Philadelphia and Washington, D.C., on Wednesday, according to the National Weather Service.

Driving the news: The coast to coast smoke, which is clearly visible from space, is due to the nearly 300 wildfires burning in British Columbia and the more than 80 large blazes in the U.S.

  • The towering pyrocumulus clouds coming off these fires is lofting smoke all the way into the stratosphere, and the jet stream is carrying the smoke eastward across the country.

Our thought bubble: Due to the presence of small particulate matter, wildfire smoke can be hazardous to human health, even many, many miles downwind. The fires are also a source of carbon dioxide emissions, thereby acting to worsen global warming.

By the numbers: Smoke from the fires blanketed New York City sending its air quality index to an 170 before dropping to a still-unhealthy 158 on Tuesday — second only to the AQI of 174 in Krasnoyarks, Russia.

  • Boston, Massachusetts, and Hartford, Connecticut, also recorded unhealthy AQI readings that were higher than 150 on Tuesday.

Context: The wildfires, many of which started when a severe heat wave erupted in June, have been linked by scientists to human-caused climate change.

In photos:
A haze over the Manhattan skyline on July 20. Photo: Spencer Platt/Getty Images
Sunlight interacting with wildfire smoke, causing the sun to appear with a reddish-orange tint in New York City on July 20. Photo: Lokman Vural Elibol/Anadolu Agency via Getty Images
The Statue of Liberty barely visible in the distance in New York City on July 20. Photo: Spencer Platt/Getty Images

Editor's note: This story has been updated throughout.

Go deeper

Wildfires mushroom in West amid heat, drought, prompting evacuations

Pyrocumulonimbus cloud towers over the Dixie Fire on Monday afternoon, seen via a California wildfire camera. (PG&E wildfire camera.)

Wildfires across the West dramatically increased in size from Monday through Tuesday, with 83 large blazes now burning in the U.S. and about 300 to the north in British Columbia.

Why it matters: The western wildfire season has kicked into high gear about two months early, as climate change-related drought and heat waves have dried out vegetation to levels not typically seen prior to late summer. About 20,000 firefighters are already deployed to blazes.

Updated Jul 20, 2021 - Science

FEMA chief heads West as large wildfires rage, heat wave peaks

Fire engulfs trees at the Tamarack fire in Central California on Saturday. Photo: Ty O'Neil/SOPA Images/LightRocket via Getty Images

FEMA administrator Deanne Criswell will make her first trip to wildfire-affected states amid another dangerous week of extreme heat and "critical" fire weather conditions, Axios has learned.

Why it matters: The West is experiencing its worst drought this century, and repeated, extreme heat waves have dried out forests and grasslands, priming them to burn. Officials are gearing up for an unprecedented, prolonged peak fire season.

Resources pushed to limit as wildfires burn across U.S. and Canada

A helicopter flies with a load of water to the Bootleg Fire, near Bly, Oregon. Photo: Payton Bruni/AFP via Getty Images

Fire officials are seeing resources stretched to the limit as scores of wildfires burn across the U.S. and Canada amid hot, dry conditions.

Threat level: In Oregon, officials have called in firefighting support from outside the Pacific Northwest — as the biggest blaze in the U.S., the Bootleg Fire, swelled to 537 square miles Monday.