Is the end in sight for recent round of Canadian wildfire smoke?

Dozens of wildfires burning in southern Canada produced smoke that traveled over the Great Lakes and Northeast during the workweek.

NEW YORK CITY – A northerly to northwesterly flow that ushered in rounds of smoke during the workweek could relax over the July 4th weekend, leading to an improvement in air quality readings.

Dozens of wildfires burning in southern Canada produced smoke that traveled over the Great Lakes and Northeast during the workweek.

The unhealthy air caused health advisories to be issued for many communities and more than 120 million Americans were put under Air Quality Alerts on Thursday, and unhealthy levels of air quality lingered across much of the inland Northeast, Great Lakes, and mid-Atlantic states early Friday morning.

Washington, Pittsburgh, Philadelphia, Cleveland, Detroit and Milwaukee all had AQI readings over 150 early Friday morning, with readings around or just under 150 in the New York City area.

Meanwhile, air quality was significantly improved Thursday night and Friday across much of Illinois south of Chicago, Indiana, western Ohio and Kentucky after Thursday’s ferocious winds associated with a derecho cleaned out the atmosphere.

Even with the help from the derecho, Cleveland woke to smokey skies on Friday where air quality alerts remain in place across northeast Ohio.

Hazy skies had returned to New York City Thursday, and FOX Weather senior meteorologist Greg Diamond said the smoke moved in quickly, and there was a campfire-like smell in the air.

Air Quality Index values did not reach levels experienced earlier in the month when records were set due to the thick smoke, but still exceeded 150, which is considered unhealthy levels.

Observation sites in the NYC metro reported an AQI of greater than 400 in June, setting a new modern record for the poorest air.

AIR QUALITY TRACKER: HOW BAD IS THE SMOKY AIR IN YOUR AREA AND WHAT’S THE SMOKE FORECAST?

Where is the smoke headed?

According to forecast models, Friday could be the final day of thick smoke for the Northeast and Great Lakes before the latest round starts to thin over the weekend.

The worst AQI values are expected to be found over Pennsylvania and upstate New York. Altoona, Pennsylvania had an AQI just over 200 Friday morning, signaling "very unhealthy" air quality. 

The AQI scale starts at 0 and runs to 500, with values of 50 or below representing cleaner air and values over 300 considered to be hazardous.

For some communities on Friday afternoon, AQI readings may drop into the unhealthy range, and health experts warn individuals should their limit outdoor activity to reduce effects.

Sensitive health groups may experience respiratory problems and difficulty breathing.

"As we get into your Saturday morning, you can start to see the smoke disperse even more with maybe a slight haze in the sky," said FOX Weather meteorologist Kelly Costa.

AIR QUALITY TRACKER: HOW BAD IS THE SMOKY AIR IN YOUR AREA AND WHAT’S THE SMOKE FORECAST?

Repetitive scenes

More than 120 million Americans were under air quality alerts on Wednesday due to the smoke as alerts stretched over 1,000 miles from Iowa to Massachusetts and down through the Carolinas and Georgia.

Cities such as Chicago, Indianapolis, Cleveland, Pittsburgh and Philadelphia all experienced poor air quality and reduced visibility.

Some of the poorest Air Quality Index readings were in Northeast Ohio, where several communities reported an AQI value above 300 at one point.

Reductions in visibility couldn’t come at a worse time for passengers, as AAA expects record travel for the Independence Day weekend.

Canada’s Toronto Pearson International Airport reported delays of more than an hour on Wednesday, which included many flights to the U.S.

BEFORE-AND-AFTER PHOTOS SHOW DRAMATIC IMPACT OF CANADIAN WILDFIRE SMOKE IN CHICAGO, DETROIT, MILWAUKEE

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Wildfire smoke turned the sky orange during sunrise in Syracuse, New York, on June 29, 2023. (@Tomismoney1/Twitter)

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This photo shows a hazy sunrise in Culpeper, Virginia, on June 29, 2023. (@ADyeMusicology/Twitter)

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A smoky sunrise over the foggy Lehigh River in Jim Thorpe, Pennsylvania, on June 29, 2023. (Mike Stanislaw/Twitter)

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Wildfire smoke turns the sky orange above Hubertus, Wisconsin, on Wednesday, June 29, 2023. (Eileen Worman via Storyful)

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CHICAGO, ILLINOIS - JUNE 28: Wildfire smoke clouds the skyline on June 28, 2023 in Chicago, Illinois. The Chicago area is under an air quality alert as smoke from Canadian wildfires has covered the city for a second straight day. (Scott Olson)

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The Chicago skyline is barely visible on June 28, 2023. ( )

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MINNEAPOLIS, MN. - JUNE 2023: Smoke from Canadian wildfires is seen from Boom Island Park on Tuesday, June 27, 2023 in Minneapolis, Minnesota. Smoke from two different regions in Canada has combined to once again make the air unhealthy in Minnesota. (Photo by Leila Navidi/Star Tribune via Getty Images) ( )

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Buildings as smoke from Canada wildfires creates haze in Chicago, Illinois, US, on Tuesday, June 27, 2023. Smoke from wildfires burning in Canada are leading to very hazy conditions and prompting air quality alerts in the Chicago area Tuesday. Photographer: Jamie Keleter Davis/Bloomberg via Getty Images ( )

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Buildings as smoke from Canada wildfires creates haze in Chicago, Illinois, US, on Tuesday, June 27, 2023. Smoke from wildfires burning in Canada are leading to very hazy conditions and prompting air quality alerts in the Chicago area Tuesday. Photographer: Jamie Keleter Davis/Bloomberg via Getty Images ( )

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ST LOUIS, MISSOURI - JUNE 27: Smoke from the Canadian wild fires can be seen in the air as Paul Goldschmidt #46 of the St. Louis Cardinals returns to the dugout during the seventh inning of a game against the Houston Astros at Busch Stadium on June 27, 2023 in St Louis, Missouri. (Photo by Dilip Vishwanat/Getty Images) ( )

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Chicago's skyline is seen from the 360 Chicago Observation Deck of the John Hancock Building with heavy smoke from the Canadian wildfires blanketing the city, on June 27, 2023, in Chicago, Illinois. Chicago Mayor Brandon Johnson said in a statement, "The City of Chicago is carefully monitoring and taking precautions as the US Environmental Protection Agency (EPA) has categorized our Air Quality Index as "unhealthy" due to Canadian wildfire smoke present in the Chicago region. We recommend children, teens, seniors, people with heart or lung disease, and individuals who are pregnant avoid strenuous activities and limit their time outdoors."  (KAMIL KRZACZYNSKI / AFP)