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The worst of Canada's wildfire smoke hit Philadelphia 1 year ago. Could it happen again?

What are the health impacts of poor air quality from wildfire smoke?
What are the health impacts of poor air quality from wildfire smoke? 03:14

PHILADELPHIA (CBS) -- Hard to believe it has been a year since Philadelphia took center stage as smoke from the Canadian wildfires left the city with the worst air quality on the planet for a day.

During June 2023 smoke from a record number of Canadian wildfires drifted south across the region.

This graphic aired during the CBS Philadelphia news shows in June 2023, a few days after the city's air quality was rated worst in the world due to Canadian wildfire smoke. CBS News Philadelphia

By June 8, the air quality over Philadelphia was so bad the sky turned a deep orange-red color and visibility dropped to less than a mile. That morning our air quality reached the highest level on the Air Quality Index (AQI) scale, with an AQI between 425pm and 500pm.

At that time on planet Earth, Philadelphia had the highest AQI level with air quality worse than spots in India, China and Eastern Europe. Many government offices, schools and businesses were closed. 

Transportation was limited as sports and activities were canceled and everyone was advised to stay indoors  – and to not spend time outdoors without proper masks.

Anything over 300pm is considered dangerous air to breathe. The AQI scale has six levels, with Hazardous (maroon color) being the highest. At that level, everyone is affected, and a health warning or emergency is declared. And that's exactly what happened for Philadelphia and most of the northeast including New York, Boston and Washington DC.

The air quality index for particle pollution is broken into six categories: good, moderate, unhealthy for sensitive groups, unhealthy, very unhealthy and hazardous. CBS News Philadelphia

Canada's 2023 wildfire season was their worst on record. Over 6,500 wildfires scorched more than 71,000 square miles of land (18.4 million hectares) between the Pacific and Atlantic oceans. 

No part of Canada was spared. What made the fire season even worse was the size of each individual fire. 

Considered megafires, they ranged from tens of thousands of acres to more than 1 million acres. The fire season also began earlier than normal and lasted far beyond the end of a typical wildfire season. 

Some of the fires became what is known as "zombie fires." Those are fires that continue slowly burning or smoldering under the loose soil, ready to surface and grow quickly under the right conditions.


What caused the Canadian wildfires? What are conditions like in 2024?

Fire conditions in Canada include extreme drought and warm temperatures with unchecked plants and trees to act as fuel. Most of last year's fires began from lightning strikes, and this year is shaping up to be another dry and hot season.

To date, in 2024 there have been 1,388 fires in Canada with an estimated 469,000 hectares burned.

More resources have been dedicated to this year's fire season and it currently rates its driest areas in British Columbia, southern Alberta, the far Northwest Territories and northern Quebec. This will likely shift and expand.

Maps from 2023 showed the smoke that blanketed the Philadelphia region blew down hundreds of miles from fires burning in the provinces of Quebec and Ontario.

A map from the Canadian Wildfire Information System shows multiple fires burning in northern Quebec once again this year, including multiple "out of control" fires.

What is the current air quality in Philadelphia?

A map of the United States shows where smoke is building in the atmosphere. Skies are clear over much of the Northeast U.S. including Philadelphia, New York and Washington D.C. while there is some smoke over Arizona, Utah and parts of Texas and New Mexico. CBS News Philadelphia

As we look back on what happened a year ago and what could be on the horizon, it's important to note that we have a good and healthy air quality on Saturday.

Currently, our air quality is 40 pm, the lowest level (green) on the AQI scale, and is considered healthy air.  

Could we see a repeat of last year's smoke over Philadelphia? 

It is possible if conditions in Canada worsen and wind patterns direct smoke toward us.

Stay up-to-date on the latest air quality and smoke conditions with our NEXT Weather Alert team of meteorologists.

The video at the top of this article was originally posted in 2023.

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